JPH0957071A - Immersion-type membrane separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immersion-type membrane separator with a cake on the membrane surface efficiently removed. SOLUTION: Plural flat membranes 11 each formed by covering the surface of a membrane support with a filter membrane are arranged at regular intervals to constitute a flat-membrane module, and only the permeated liq. is sucked in from one or both ends of the membrane. The module is dipped in a tank 10, and a diffuser pipe 15 is set below the flat membrane in this immersion-type membrane separator. A spongy or brushy scraper 12 moved vertically along with the water level between the membranes 11 in the tank or by a float with water introduced or discharged into or from it is provided in parallel and in contact with the membrane 11.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, membrane separation has been accompanied by technological development, not only solid-liquid separation in chemical and food production lines, but also water production.
It is widely applied to the recovery of organic substances from wastewater, solid-liquid separation of tap water, gray water, and human waste, and is about to be applied 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 the stock solution is supplied to the inside of the membrane module while pressurizing it with a pump, and the stock solution discharged without passing through the membrane is supplied to the inside of the membrane module again. The liquid circulation method is adopted. In this liquid circulation system, the cake layer on the membrane surface that causes filtration resistance is reduced as much as possible, and the circulation rate of the stock solution is increased by a pump to keep the filtration amount constant and the membrane surface speed is increased. There is. However, if the circulation amount of the stock solution is increased, the membrane module is pressurized, so that the membrane is likely to be clogged, resulting in high pressure loss,
The filtration rate will decrease. Further, the circulation amount of the stock solution reaches about 100 times the filtration amount, and the operating cost becomes high. This makes it difficult to apply to wastewater treatment, which requires low running costs.

On the other hand, an immersion method has been developed in which the membrane is entirely filtered while being immersed in the stock solution tank. This method is a method that suppresses the accumulation of cake on the membrane surface by filtering at a transmembrane pressure lower than that of the liquid circulation method, instead of giving no flow of the undiluted solution on the membrane surface. It is possible to drive. Further, since the structure is simple, there is an advantage that maintenance is easy. In order to generate a pressure difference between the membranes for filtration, the suction method is often used because it is less clogged than the pressure method and only requires the membrane to be immersed in the stock solution tank. The cake adhering to the film surface is peeled off and removed by bubbling while supplying air from an air diffusing tube or air diffusing plate provided in the lower part of the film. However, even if air bubbling is adopted, there are cases where the removal or peeling of the cake on the film surface is not sufficient, and a large film area is required to compensate for this, which causes a problem of cost increase.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a submerged membrane separator capable of solving the above-mentioned problems of the prior art and efficiently removing the cake on the membrane surface.

[0005]

According to the present invention, a sponge-like or brush-like scraper is provided between flat membranes so as to be in parallel with the flat membranes and slightly in contact with the flat membranes, and the scrapers are moved up and down. The above problem is solved by making it movable. That is, the immersion-type membrane separation device of the present invention has a plurality of flat membranes in which the surface of a membrane support is coated with a filtration membrane is arranged at equal intervals, and only the permeated liquid can be sucked from both ends or one end of the flat membrane. In a submerged membrane separator in which a membrane module is immersed in a tank and an air diffuser is installed below the flat membrane, a sponge-like or brush-like scraper that moves up and down with the water level in the tank between the flat membranes. Is provided so as to be in contact with the flat membrane in parallel with the flat membrane. The present invention
Further, a plurality of flat membranes having the surface of the membrane support coated with a filtration membrane are arranged at equal intervals, and the flat membranes capable of sucking only the permeated liquid from both ends or one end of the flat membrane are immersed in a tank, In a submerged membrane separation device with an air diffuser installed underneath, a sponge-like or brush-like scraper that moves up and down with a float that allows water to enter and drain between the flat membrane and the flat membrane. The present invention provides an immersion type membrane separation device, which is provided so as to come into contact with a flat membrane.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the immersion-type membrane separation device of the present invention, a plurality of flat membranes, each having a surface of a membrane support coated with a filtration membrane, are arranged at equal intervals. The membrane support is not particularly limited and any one can be used, and examples thereof include a porous support such as a membrane support net and a flat plate.

In the present invention, a scraper is installed between the flat membranes as described above so as to be vertically movable while being parallel to the flat membranes and in contact with the flat membranes. The vertical movement of the scraper
Some are due to the water level and some are due to the ingress or egress of water into the float associated with the scraper. In either case, the scraper need not rotate.

The vertical movement of the scraper depending on the water level can be performed by connecting the scraper to the float. In this type, as the float moves up and down according to the water level in the tank, the scraper also moves up and down to remove the cake adhering to the film surface.

On the other hand, the vertical movement of the scraper by infiltration or discharge of water into the float connected to the scraper is performed by the following method. That is, by injecting the air in the float, water enters the float, the weight of the float and scraper sinks, and when the water sinks to the lower end of the flat membrane, the air is pressed into the float and the water inside the float Is gradually discharged, the float and scraper gradually float up.

[0010]

EXAMPLES The present invention will now be described in detail based on examples with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a schematic system diagram of an immersion type membrane separation apparatus showing a first embodiment of the present invention, and FIG. 2 is an explanatory view showing a scraper installation state in the membrane separation apparatus shown in FIG. In the membrane separation apparatus shown in FIG. 1, a plurality of flat membranes 11 having both sides of a membrane support coated with microfiltration membranes are arranged at equal intervals, and the flat membranes 11 capable of sucking only permeate are separated. It is immersed in the tank 10. As shown in FIG. 2, a brush-shaped scraper 12 is placed between the flat membranes 11 so that the flat membranes 11 are slightly in contact with each other.
A float 16 for floating the scooper 12 is connected to both sides of the float 16, and the float 16 moves up and down depending on the water level in the separation tank 10. A plurality of air diffusers 15 are provided in parallel with the flat membrane 11 so that the air for bubbling cleaning reaches the entire membrane under the flat membranes. The air is supplied by the blower 22 so that it can be injected into the separation tank 10 from the lower portion of the flat membrane 11.

When performing membrane separation, first, a stock solution containing a suspension is supplied from the stock solution inlet 13 to fill the inside of the separation tank 10, and then the stock solution is circulated through the stock solution circulation outlet 14. Next, the suction pump 20 is operated, the electromagnetic valve 21 is opened, and suction filtration is performed. The suspension in the stock solution adheres to the flat membrane 11 surface by suction filtration, and becomes a cake layer while accumulating. If suction filtration is continued, the cake layer becomes thicker, or the cake layer is consolidated, and the suction pressure of the pressure gauge 24 rises, the transmembrane differential pressure increases, and the permeation amount measured by the flow meter 25 decreases. When it becomes equal to or higher than an arbitrary transmembrane pressure difference or lower than an arbitrary permeation amount, the suction pump 20 is stopped and the filtration is stopped.

Next, air is bubbled and washed to remove and remove the cake on the surface of the flat film 11. In the bubbling cleaning, first, the blower 22 is operated, the electromagnetic valve 23 in the air pipe is opened, and the air from the air diffuser pipe 15 is supplied at a predetermined air amount.
Perform for a predetermined time. The supplied air peels and removes the cake on the surface of the flat film 11 while rising as a gas-liquid mixed solution with the stock solution and rising. After bubbling cleaning, suction pump 20 again
To start filtration.

When the transmembrane pressure difference and the permeation amount do not recover even after repeating the above-mentioned operation by bubbling and washing, it is judged that the cake on the membrane surface is not easily peeled off, suction filtration is stopped, and the separation tank 10 is separated. Pull out the undiluted solution and gradually lower the water level. Along with this, since the scraper 12 is provided with the float 16, the brush of the scraper 12 is gradually lowered while slightly contacting the flat film 11 along with the water surface, and the cake is peeled off. When the scraper 12 reaches the bottom of the flat membrane 11, the stock solution is again supplied to the separation tank 10 to gradually raise the water level. Similar to when the water level is lowered, the brush of the scraper 12 slightly contacts the flat film 11 and gradually rises, and the cake is further peeled off. When the scraper 12 returns to the original position, the solenoid valve 21 is opened, the suction pump 20 is operated, and filtration is started. By providing the scraper 12 between the flat membranes 11 as described above, it is possible to easily remove the cake on the membrane surface that could not be peeled or removed even by bubbling cleaning.

FIG. 3 is an explanatory view of a scraper of an immersion type membrane separation device showing a second embodiment of the present invention. In FIG. 3, the scraper 12 is connected to a pair of floats 26. The float 26 has a water inlet / outlet 27 and an air inlet / outlet 28, and the air inlet / outlet 28 is connected to a compressor 30 via a three-way valve 29. Has been done.

Membrane separation and bubbling cleaning are carried out in the same manner as described above, but at that time, the float 26 is blown with air from the compressor 30 so that the float 26 is filled with air and floated on the water surface. After bubbling cleaning, stop the compressor 30, open the three-way valve 29, and float 2
The air in 6 is released to the atmosphere. At this time, water intrudes into the float 26 through the water inlet / outlet 27 as the air is discharged, and the float 26 sinks due to its weight. Float 26
When the inside is filled with water, the scraper 12 reaches the lower part of the flat film 11. After that, the compressor 30 is operated, air is blown into the float 26 from the air inlet / outlet 28, and water is discharged.
6 starts to surface. Also in this embodiment, when the float 26 moves up and down as water enters and leaves the float 26, the scraper 12 swings up and down while slightly contacting the flat film 11,
As a result, the cake attached to the flat film 11 is completely peeled and removed.

Comparative Example In order to confirm the state of peeling and removal of the cake from the surface of the membrane when bubbling cleaning was performed with air, a flat membrane in which both sides of the membrane support were coated with a microfiltration membrane was used. The stock solution of the system was suction filtered by constant flow rate filtration. When the specified transmembrane pressure difference is reached, after stopping filtration, air is removed from the bottom of the flat membrane by 3
L / min / m ² -Supplied over the membrane area and bubbling washed. After washing for 3 minutes, the stock solution in the separation tank was pulled out, and it was found that the cake was still attached to the membrane surface in many places. Further, in order to peel off and remove the cake on the film surface, it is necessary to perform washing for a long time.

[0017]

EFFECT OF THE INVENTION By using the membrane separation device of the present invention, the cake on the membrane surface can be always removed, and the suspended matter in the waste liquid containing the suspended matter can be efficiently membrane-separated.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing an installed state of a scraper in the membrane separation device shown in FIG.

FIG. 3 is an explanatory diagram of a scraper of a membrane separation device showing a second embodiment of the present invention.

[Explanation of symbols]

 10 Separation Tank 11 Flat Membrane 12 Scraper 13 Raw Liquid Inlet 15 Diffuser 16 Float 20 Suction Pump 22 Blower 26 Float 27 Water Inlet / Outlet 28 Air Inlet / Outlet 30 Compressor

Claims (2)

[Claims] 1. A flat membrane module in which a plurality of flat membranes each having a surface of a membrane support coated with a filtration membrane are arranged at equal intervals, and only a permeated liquid can be sucked from both ends or one end of the flat membrane is immersed in a tank. Then, in the immersion type membrane separation device in which an air diffuser is installed at the bottom of the flat membrane, a sponge-like or brush-like scraper that moves up and down with the water level in the tank between the flat membrane and the flat membrane in parallel with the flat membrane. An immersion-type membrane separation device, which is provided so as to come into contact with a flat membrane. 2. A flat membrane module in which a plurality of flat membranes each having a membrane support surface coated with a filtration membrane are arranged at equal intervals so that only permeate can be sucked from both ends or one end of the flat membrane is immersed in a tank. Then, in the immersion type membrane separation device in which the air diffuser is installed at the bottom of the flat membrane, a sponge-like or brush-like scraper that moves up and down by a float that allows water to enter and discharge between the flat membrane and the flat membrane, An immersion type membrane separation device, which is provided so as to be in contact with the flat membrane in parallel with the flat membrane.