JPH09141065A - Dipping type membrane separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stable and continuous operation of a dipping type membrane separation device for a long time with a high permeation flux of about >=0.6m<3> / m<2> .day while preventing deposition of a cake layer on the membrane surface. SOLUTION: After a flocculant is added to the raw water in a flocculating tank 1, the water is introduced into a membrane dipping tank 2 equipped with flat membrane modules 3 and an aerating tube 5. The distance between adjacent flat membrane modules is specified to 10-15mm. Since the water is sufficiently treated for flocculation by adding a flocculant in the flocculating tank independently from the tank 2 and then introduced into the tank 2, such a problem that a flocculant unused for the reaction is sucked to cause clogging of membranes can be avoided. Since the distance between flat membrane modules is rather large as 10-15mm, the device can be stably operated for a long time even with rather high permeation flux of >=0.6m<3> /m<2> .day without deposition of a cake layer on the membrane surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion type membrane separator, and more particularly to an immersion type membrane separator capable of preventing a cake layer from adhering to the surface of a membrane and obtaining a high permeation flux. .

[0002]

2. Description of the Related Art Conventionally, in various sludge treatment processes,
The membrane module is immersed in the aeration tank, the membrane permeate is sucked from the membrane module, and the air lift circulation flow velocity generated by aeration from below is applied to prevent the cake layer from adhering to the membrane surface. An immersion type membrane separation device for performing the above is known.

In such an immersion type membrane separator,
It is desired to prevent the cake layer from adhering to the membrane surface and to improve the treatment efficiency by operating at a higher permeation flux.

Conventionally, for the purpose of preventing the cake layer from adhering and improving the permeation flux in the immersion type membrane separator, a flat membrane module is provided in the aeration tank, and a certain distance is provided between the lower portion of the flat membrane module and the aeration means. It has been proposed that the flat membrane module has a membrane spacing of 6 to 10 mm and that a coagulant is added to the aeration tank.

The above-mentioned submerged membrane separation apparatus mainly targets activated sludge.

By the way, generally, in a pressure type tubular membrane module or flat membrane module, even if the same membrane module is used for separating activated sludge and for separating aggregated sludge, it is used for separating aggregated sludge. If you do 2
In many cases, it is possible to operate with a permeation flux that is twice as high.

This is because in the separation of activated sludge, the high molecular weight organic substances present in the activated sludge mixture form a gel layer on the membrane surface, which becomes a large resistance in membrane permeation, whereas in the separation of coagulated sludge, This is because the addition of the inorganic coagulant coagulates and removes the high molecular weight organic matter in the liquid, and thus the formation of the gel layer on the film surface is reduced.

Therefore, it is presumed that even in the above-mentioned submerged membrane separation apparatus, the permeation flux can be further increased when it is used for separating coagulated sludge.

[0009]

However, even when the coagulated sludge is separated by the above-mentioned submerged membrane separation device, in actuality, as in the case of the activated sludge separation, 0.6 m ³
It is possible to operate only with a permeation flux of less than / m ² · day. This is because when used for separating coagulated sludge, the gel layer is less likely to form on the membrane surface, so if the number of days is short, operate at a high permeation flux of 0.6 m ³ / m ² · day or more. However, if the operation is continued at a high permeation flux for a long period of time, the concentration rate of sludge on the membrane surface will increase.
This is because, at a film interval of 10 mm, the cake layer becomes significantly attached in addition to the gel layer, and the cake layer becomes a large resistance in membrane permeation.

On the other hand, in the above-mentioned immersion type membrane separation apparatus in which the coagulant is directly added to the aeration tank in which the membrane module is immersed, unreacted coagulant is also sucked at the time of sucking the membrane permeated water, thus clogging the membrane. Occurs, and high permeation flux cannot be achieved.

The present invention solves the above conventional problems and prevents the cake layer from adhering to the membrane surface for a long time even when the membrane permeation flux is set to a high value of 0.6 m ³ / m ² · day or more. It is an object of the present invention to provide an immersion type membrane separation device that can continue stable operation over a period of time.

[0012]

Means for Solving the Problems An immersion-type membrane separation device of the present invention comprises a membrane dipping tank, a membrane surface in the membrane dipping tank in the vertical direction, and adjacent membrane modules being parallel to each other. A plurality of flat sheet membrane modules which are immersed and arranged at a predetermined interval, an aeration means provided below the flat sheet membrane module in the membrane immersion tank, and a suction means for sucking the membrane permeated water of the flat sheet membrane module. In a submerged membrane separation device comprising a coagulation tank for adding a coagulant to raw water, and means for introducing the effluent of the coagulation tank into the membrane immersion tank,
The space between the adjacent flat sheet membrane modules is 10 to 15 mm.

In the immersion type membrane separation apparatus of the present invention, the coagulant is added in a separately provided coagulation tank without directly adding the coagulant into the tank in which the membrane module is immersed, and a sufficient coagulation treatment is performed. Since the coagulation treatment liquid is introduced, there is no problem of clogging of the film due to suction of the unreacted coagulant.

Further, the interval between the flat sheet membrane modules is 10 to 15
Since it is relatively large, the adhesion of the cake layer tends to dominate the permeation flux rather than the formation of the gel layer on the membrane surface as compared with the membrane separation of activated sludge.
Even when operating with a high permeation flux of 0.6 m ³ / m ² · day or more, stable operation can be performed for a long period of time without depositing a cake layer on the membrane surface.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of the immersion type membrane separation apparatus of the present invention, and FIG. 2 is a perspective view for explaining the arrangement of the flat sheet membrane module of the present invention. In FIGS. 1 and 2, 1 is a flocculation tank, 2 is a membrane dipping tank, 3 is a flat membrane module, 4 is a suction pump for sucking the permeated water of the flat membrane module 3, and 5 is a flat membrane module 3 of the membrane dipping tank 2. Each reference numeral of 11 to 15 is a pipe for performing aeration from below. Reference numeral 6 denotes a nozzle for taking out the permeated water of the flat sheet membrane module 3, which is connected to the pipe 14.

In the immersion type membrane separation apparatus of this embodiment, first,
Raw water is introduced into the coagulation tank 1 through the pipe 11, and a coagulant is added from the pipe 12 in the coagulation tank 1 to perform coagulation treatment.

As the coagulant, an inorganic coagulant such as a sulfuric acid band (aluminum sulfate) or polyaluminum chloride is generally used, and the addition amount thereof is generally about 100 to 5000 mg / L with respect to the raw water. Is preferred.

The coagulation treatment liquid is introduced into the membrane immersion tank 2 through the pipe 13 and subjected to the membrane separation treatment by the flat membrane module 3.

That is, the coagulation treatment liquid introduced into the membrane dipping tank 2 becomes a circulating flow due to aeration by the diffuser tube 5, and the membrane permeated water that has permeated the membrane by the suction of the suction pump 4 on the membrane surface of the flat membrane module 4. Is taken out from the pipe 14 through the nozzle 6.

From the membrane dipping tank 2, the membrane dipping tank 2 is connected through the pipe 15 so that the sludge concentration in the membrane dipping tank 2 becomes a predetermined concentration.
Sludge (concentrated water) stored at the bottom of the is continuously or intermittently withdrawn.

In the present invention, in such an immersion type membrane separation device, the distance d between the adjacent flat membrane modules 3 is set to 10 to 15 mm. By setting the distance d to be 10 mm or more, which is relatively large, it is possible to prevent the cake layer from adhering to the film surface. When the distance d is less than 10 mm,
Such effects cannot be sufficiently obtained. Even if the distance d is set to be larger than 15 mm, there is almost no difference in the effect of preventing the cake layer from adhering, and the increase in the installation interval of the membrane modules reduces the number of membrane modules arranged per unit volume, which is not preferable.

In the present invention, as the membrane of the flat membrane module, an ultrafiltration membrane, a microfiltration membrane or the like is generally used.

The immersion type membrane separation apparatus of the present invention as described above is
In particular, it is suitable for treating undiluted activated sludge membrane separation water of human waste, industrial wastewater, etc., and generally has a membrane permeation flux of 0.6 m ³ / m ² · day or more, for example, 0.8 to 1.2 m ^3. Even when the treatment is continued with a membrane permeation flux of / m ² · day, it is possible to prevent the cake layer from adhering to the membrane surface and continue the treatment for a long time.

[0025]

The present invention will be described more specifically with reference to the following examples.

Example 1 In the immersion type membrane separation apparatus shown in FIG. 1, the membrane modules were separated at intervals of 5 mm, 10 mm, 15 mm and 20 mm, and the membrane separation was performed under the same conditions.

The liquid to be treated is undiluted activated sludge membrane separation treated water of night urine, to which liquid sulfuric acid band as an inorganic coagulant in the coagulation tank 1 (8% by weight Al ₂ O ₃ aqueous solution).
Was added at 3000 mg / L for aggregation treatment, and the aggregation treatment liquid was allowed to flow into the membrane dipping tank 2.

The concentration of coagulated sludge in the membrane dipping tank 2 is 15,000.
The amount of sludge drawn out was adjusted to be about mg / L.

The set permeation flux of each membrane separator is 0.6, 1.0, 1.5, 2.0 m ³ / m ² ·, as shown in FIG.
The pressure was gradually increased with the lapse of time, and the daily change of the suction pressure at this time was examined. The results are shown in FIG.

The following is clear from FIG.

That is, in the operation with a permeation flux of 0.6 m ³ / m ² · day, the suction pressure increased only after about 1 month when the membrane module spacing was 5 mm. There was adhesion.

[0032] The operation in the permeation flux 1.0 m ³ / m ² · day or more has been performed for more than membrane module spacing 10 mm, the permeation flux 1.0 m ³ / m which the membrane separation device in ^two-days Although the suction pressure did not rise for 2 months, the suction pressure increased only for about 2 months when the permeation flux was 1.5 m ³ / m ² · day and the membrane module spacing was 10 mm. I was seen. Also, the permeation flux of 2.0 m ³ / m ² ·
In the daily operation, the suction pressure increased for the membrane module intervals of 15 mm and 20 mm in about 10 days.

From the above results, when the membrane module spacing of the coagulation membrane separation device is set to 10 mm or more, the permeation flux of 0.
It was confirmed that long-term operation at 6 to 1.0 m ³ / m ² · day was possible, and that there was almost no difference in terms of preventing cake layer adhesion between the membrane module intervals of 15 mm and 20 mm.

[0034]

As described above in detail, according to the submerged membrane separation apparatus of the present invention, even when a high permeation flux of 0.6 m ³ / m ² · day or more is set, the surface of the membrane is not affected. It is possible to effectively prevent the cake layer from adhering to continue the operation stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of an immersion type membrane separation device of the present invention.

FIG. 2 is a perspective view showing a membrane module arrangement according to the present invention.

FIG. 3 is a graph showing changes with time of permeation flux and suction pressure in Example 1.

[Explanation of symbols]

 1 Coagulation tank 2 Membrane immersion tank 3 Flat membrane module 4 Suction pump 5 Air diffuser

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C02F 11/12 C02F 11/12 E

Claims (1)

[Claims] 1. A membrane dipping tank and a plurality of flat plates immersed in the membrane dipping tank at predetermined intervals so that the membrane surfaces are in the vertical direction and adjacent membrane modules are parallel to each other. In a submerged membrane separation device comprising a membrane module, an aeration means provided below the flat membrane module in the membrane dipping tank, and a suction means for sucking the membrane permeated water of the flat membrane module, A dipping type characterized in that a coagulation tank for adding a coagulant and a means for introducing the effluent of the coagulation tank into the membrane dipping tank are provided, and the interval between the adjacent flat membrane modules is set to 10 to 15 mm. Membrane separation device.