JP3446399B2 - Immersion type membrane separation device and membrane separation method using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a submerged membrane separation device, and more particularly, to a submerged membrane separation device for efficiently separating a suspension in wastewater by using a microfiltration membrane, an ultrafiltration membrane and the like. The present invention relates to a membrane separation method.

[0002]

2. Description of the Related Art Recently, membrane separation has been carried out not only in solid-liquid separation of chemical and food production lines, but also in production of water, recovery of organic substances from wastewater, solidification of tap water, gray water and human waste as technology advances. It is widely applied to liquid separation, and even to the treatment of sewage and industrial wastewater. In the conventional membrane separation device, a tubular or plate-shaped membrane is used in the membrane module, and while supplying the raw solution while pressurizing the inside of the membrane module with a pump, the raw solution discharged without permeating the membrane. A liquid circulation system is adopted in which the water is again supplied to the inside of the membrane module. In this liquid circulation system, the cake layer on the membrane surface that causes filtration resistance is reduced as much as possible, and in order to keep the filtration rate constant, the circulation rate of the undiluted solution is increased by the pump to increase the membrane surface flux. ing.

However, if the circulation amount of the stock solution is increased, the membrane module is pressurized, so that the membrane is apt to be clogged, the pressure loss increases, and the filtration amount decreases. Further, the circulation amount of the stock solution reaches about 100 times the filtration amount, resulting in high operating cost. This makes it difficult to apply to wastewater treatment, which requires low running costs.

However, recently, an immersion method has been developed in which the entire amount is filtered while the membrane is immersed in the stock solution tank. This is a method of suppressing the accumulation of cake on the membrane surface by filtering at a transmembrane pressure difference lower than that of the liquid circulation method, instead of giving the flow of the undiluted solution on the membrane surface, and low-power operation is possible. It is possible. Further, since the structure is simple, there is an advantage that maintenance is easy. In order to generate a differential pressure between the membranes for filtration, the suction method is often used because it has less clogging than the pressure method and only requires the membrane to be immersed in the stock solution tank. The cake adhering to the surface of the film is peeled off by intermittently or continuously bubbling air from an air diffuser or an air diffuser plate provided at the bottom of the film. When performing this bubbling, it is considered that the cake is held on the membrane surface by suction, so it is usually desirable to temporarily stop suction filtration. However, stopping suction filtration for bubbling does not allow permeate to be obtained during this time, so effective filtration cannot be performed, and a large amount of membrane area is required to compensate for this, leading to an increase in cost. thing,
Further, there is a problem that complicated control for bubbling is required.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a submerged membrane separation apparatus which can obtain a permeated liquid even during bubbling, does not require a complicated control device, and can perform membrane separation efficiently and inexpensively. It is an object to provide a membrane separation method using this.

[0006]

Means for Solving the Problems In order to observe the clogging of the membrane of an immersion type membrane separator, both sides of a support net are covered with a microfiltration membrane so that bubbling can be performed from the bottom as shown in FIG. Then, a permeate outlet was provided at the upper part, and the inorganic stock solution was suction filtered. After filtration, air bubbling was carried out from the lower part of the flat membrane to remove the cake adhering to the membrane surface.
Then, the membrane was cut out in the longitudinal direction, and the filtration resistance of the membrane was measured. As shown in FIG. 3, the filtration resistance was higher as it was closer to the permeate outlet, and tended to decrease with distance. From this, it was found that the filtration amount was larger as it was closer to the permeate outlet and was not effectively used as it was farther from the permeate outlet. Further, from this fact, it was found that the cake on the membrane surface was more likely to be peeled off than near the permeate outlet, because it was not sucked as far as it was far from the permeate outlet.

Therefore, permeate outlets are provided at both lateral ends and suction filtration is alternately performed, and when suction is performed from one of the permeate outlets, only the membrane surface near the other permeate outlet is air bubbled. It was found that the cake on the membrane surface can be peeled off without stopping suction filtration, and the membrane surface can be effectively used. The present invention has been completed based on such findings.

That is, the immersion type membrane separation apparatus of the present invention is
Permeate outlet is provided at both ends of the flat membrane, the respective suction pumps via the opening to the valve so as to suck the permeated liquid alternately to the permeate outlet connection, the flat membrane each of permeate below the It is divided into the outlet side and the reverse side to the side that sucks the permeate.
An air diffuser for air bubbling the flat membrane on the side is installed.

Further, according to the present invention, the separation tank of the above-mentioned immersion type membrane separator is filled with the stock solution, and the permeated liquid is suction-filtered from one permeate outlet of the flat membrane, and at the same time, the other permeate outlet is sprayed. It is intended to provide a membrane separation method characterized in that an operation of driving a gas device to perform air bubbling from below to remove the cake adhering to the membrane surface is alternately repeated.

[0010]

The present invention will now be described in detail based on embodiments with reference to the drawings. FIG. 1 is a system diagram of an immersion type membrane separation apparatus showing an embodiment of the present invention. The flat membrane 11 used here covers both sides of the membrane support net with filtration membranes, arranges a plurality of these at equal intervals, pots both edges with synthetic resin, etc., and then cuts it. Exit 1
4 and 15 are provided so that only the permeated liquid can be taken out. 12 and 13 are membrane sealing parts.

In the membrane separation apparatus shown in FIG. 1, the flat membrane 1
A plurality of 1s are arranged in parallel and immersed in the separation tank 10. Below the flat membrane 11, a plurality of air diffusers 26 and 27 are provided in parallel with the flat membrane 11 so that air bubbles can reach the entire membrane, but they are divided into the permeate outlet 14 side and the permeate outlet 15 side. The air from the blower 23 can be arbitrarily supplied to either side by electromagnetic valves 24 and 25.
Further, electromagnetic valves 21 and 22 are provided on the permeate outlet 14 side and the permeate outlet 15 side, respectively, so that the permeate can be taken out from either side.

When performing membrane separation using the membrane separation apparatus shown in FIG. 1, first, a stock solution containing a suspension is supplied from the stock solution inlet 16 to fill the inside of the separation tank 10 and then the stock solution circulation outlet 1
Circulate the stock solution through 7. Next, the suction pump 20 is operated, the electromagnetic valve 21 is opened, the electromagnetic valve 22 is closed, and suction filtration is performed from the permeate outlet 14 side. The suction degree at this time is measured by the pressure gauge 30. The suspension in the stock solution adheres to the flat membrane 11 surface on the permeate outlet 14 side by suction filtration, and becomes a cake layer while accumulating. Meanwhile, the blower 23
To open the solenoid valve 24 in the air pipe,
Is closed and air is bubbled from the diffuser pipe 27 on the permeate outlet 15 side to remove the cake on the flat membrane 11 surface on the permeate outlet 15 side.

When any time elapses, or when the transmembrane pressure difference or the permeated liquid amount is decreased, the electromagnetic valve 21 is closed and the electromagnetic valve 22 is opened to suction-filter the permeated liquid outlet 15 side. At this time, similarly to the above, the suspension in the stock solution is deposited as a cake layer on the flat membrane 11 surface on the permeate outlet 15 side. The solenoid valve 21 is closed and the solenoid valve 22 is opened. At the same time, the solenoid valve 24 in the air pipe is closed, the solenoid valve 25 is opened, and air is bubbled from the diffuser pipe 26 on the permeate outlet 14 side to the permeate outlet 14 side. The cake on the surface of the flat film 11 can be removed.

As described above, when the membrane separation device of the present invention is used, the permeated liquid is sucked in the permeated liquid outlet 14 side and the permeated liquid outlet 15 side.
By alternately repeating the process with the side and air bubbling the surface of the flat membrane 11 on the side that does not suck the permeated liquid, the cake adhering to the flat membrane 11 can always be removed without stopping suction filtration. In the above embodiment, the air diffusing tubes 26 and 27 for air bubbling are provided in parallel with the flat membrane 11, but they may be arranged so as to be orthogonal to the flat membrane 11. Further, not only the air diffusing tube but also air diffusing balls, air diffusing plates, etc. may be used as long as the air is evenly distributed over the flat membrane.

Air can be supplied to the flat membrane by various methods. As a specific example, the amount of permeation increases from the result of FIG. 3 as it approaches the permeate outlet.
When an air diffuser is provided in parallel with the flat membrane as shown in Fig. 4, the distance between the air diffusers 40 of the air diffuser is made closer to the permeate outlet as shown in Fig. 4 to adjust the air amount distribution. May be. Further, when the air diffuser is orthogonal to the flat membrane, as shown in FIG. 5, each air diffuser is provided with an air amount adjusting valve 41 to increase the opening degree of the valve closer to the permeate outlet, or As shown in FIG. 6, the distribution of the air amount may be adjusted by a method such that the distance between the air diffuser holes 40 of the air diffuser is made closer to the permeate outlet.

[0016]

EFFECTS OF THE INVENTION According to the present invention, the cake on the membrane surface can always be removed with a simple device without stopping suction filtration, and the suspension in the waste liquid containing the suspension can be removed. Membrane separation can be efficiently performed at low cost.

[Brief description of drawings]

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

FIG. 2 is an explanatory view of an immersion type flat membrane separation experiment device for confirming the filtration resistance of the membrane.

FIG. 3 is a graph showing the relationship between the distance from the permeate outlet of the membrane and the filtration resistance.

FIG. 4 is an explanatory diagram showing an example of an air diffuser that can be used in the membrane separation device of the present invention.

FIG. 5 is an explanatory diagram showing another example of an air diffuser that can be used in the membrane separation device of the present invention.

FIG. 6 is an explanatory diagram showing another example of an air diffuser that can be used in the membrane separation device of the present invention.

[Explanation of symbols]

10 separation tanks 11 flat membrane 12 Membrane seal part 13 Membrane seal part 14 Permeate outlet 15 Permeate outlet 16 Stock solution inlet 17 Stock solution circulation outlet 20 suction pump 21 Solenoid valve 22 Solenoid valve 23 blower 24 Solenoid valve 25 solenoid valve 26 Air diffuser 27 Air diffuser 30 pressure gauge 40 air diffuser 41 Air amount adjustment valve

Claims (4)

(57) [Claims] 1. Permeate outlets are provided at both ends of the flat membrane, and the permeate outlets are opened to alternately aspirate the permeate.
Is connected to a suction pump via closes valve, wherein the lower flat film is divided into the permeate outlet side of each permeate
An immersion-type membrane separation device comprising an air diffuser for air-bubbling a flat membrane on the side opposite to the suction side . 2. The submerged membrane separation apparatus according to claim 1, wherein the distance between the air diffusion holes of the air diffusion device is closer to the permeate outlet. 3. The separation tank of the immersion type membrane separator according to claim 1 is filled with the stock solution, and suction filtration of the permeate is performed from one permeate outlet of the flat membrane, and at the same time, the other permeate outlet side is sprayed. A membrane separation method, characterized in that the operation of driving the air device to perform air bubbling from below to remove the cake adhering to the membrane surface is alternately repeated. 4. The membrane separation method according to claim 3, wherein the air amount of the air bubbling is increased toward the permeate outlet.