JPH084722B2 - Membrane separation device - Google Patents

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 for easily and efficiently membrane-separating various suspensions (for example, suspensions of microbial particles, inorganic particles, etc.) to obtain a clear separation liquid. It is about.

[0002]

2. Description of the Related Art Conventionally, there is known a device in which a bundled module of hollow fiber membranes is immersed in an aeration tank to obtain a permeate (see FIG. 4).

In the apparatus shown in FIG. 4, the hollow fiber membrane module 22 is immersed in the aeration tank 21, and the air diffuser pipe 23 supplies air 24.
To keep the inside of the tank aerobic and secure the growth of microorganisms, while maintaining the filtration function of the hollow fiber membrane.
5, the permeated water 26 of the suspension in the tank treated with microorganisms is obtained from the hollow fiber membrane.

However, when the present inventor made a supplementary test of this prior art, the following serious drawbacks were recognized:
It turned out that it was not practical. That is, the device shown in FIG. 4 has the following problems.

SS particles such as activated sludge and fiber,
Enter inside the bundle of hollow fiber membranes and adhere or stick,
The filtration resistance increases rapidly. The SS component that has entered the inside of the bundle of hollow fiber membranes is extremely difficult to wash and remove, and the adhered sludge and fiber components cannot be washed and removed unless the hollow fiber membrane module is taken out and the yarn is sprayed with high-pressure water. This is a troublesome task, and it is practically impossible to perform such work.

[0006]

SUMMARY OF THE INVENTION The present invention has an object of completely solving the serious drawbacks of the above-mentioned conventional apparatus, and provides a new technique which can maintain the filtration resistance low for a long period of time and is maintenance-free. This is an issue.

[0007]

The present invention has been completed as a result of various studies in order to solve the drawbacks of the conventional techniques, and as a result, it was found that the conventional drawbacks can be solved by the following means.

That is, according to the present invention, a filter body comprising a spacer and a planar separation membrane, a tank in which one or more filter bodies are provided and which receives a suspension, a lower portion of the filter body or a lower side of the filter body. And a diffusing unit having a diffusing section disposed on one side, and a means for intermittently setting a large amount of diffusing gas per unit time from the diffusing unit. Is.

The novel idea of the present invention is as follows. The adoption of a hollow fiber membrane is stopped, and a filter body having a planar separation membrane in which SS is unlikely to enter inside the bundle is applied.

Conventionally, a method of installing a planar separation membrane in a structure such as a filter press or a dehydrator has been known, but there is no conventional concept of immersing the planar separation membrane in the aeration tank body by the method of the present invention. It was

It has been found that film contamination can be effectively prevented by intermittently increasing or decreasing the amount of air diffused for giving turbulence to the film surface. The filter body used in the present invention has a filter portion including at least a spacer and a planar separation membrane. The structure of the filter body has a function of filtering the suspension at least outside the planar separation membrane as a filtering portion and transferring the filtered water into the inside of the membrane, and further has means for taking out the transferred filtered water. The structure of the filtering unit is not particularly limited as long as it is provided. However, it is preferable that the outer shape of the filtering portion is such that the entire surface of the planar separation membrane is easily brought into contact with the bubbles supplied from the air diffuser and the water flow due to the bubbles when the filtering body is placed in the tank.

The outer surface of the filtration portion is formed of a flat separation membrane, but it is not always necessary to form the entire outer surface of the flat separation membrane. Can be formed.

The shape of the outer surface of the planar separation membrane is not particularly limited as long as the above conditions are satisfied, and is not limited to a flat surface and may include any curved surface. The structure of the spacer is arbitrary and is not particularly limited as long as it has a function of supporting the planar separation membrane and at least having a function of ensuring a space for allowing transfer into the inside of the filtered water. It is also possible to equip it with a means for taking out the transferred filtered water to the outside, for example, an outflow pipe.

The constituent material of the spacer and the specific shape and structure thereof are arbitrary, and may be a single body having a solid interior, a single body having a space inside, a frame shape, or a combination thereof. Examples thereof include a frame shape, a simple plate shape with a solid interior, a plate shape with a space provided inside, and a lattice shape. In particular,
As a constituent material, a porous body having a filtering function is preferable, and a plate-like shape is particularly preferable.

Adhesives, bolts / nuts, magnets and the like can be applied as means for supporting the planar separation membrane on the spacer. Therefore, the external shape of the filtration portion of the filter is arbitrary because it is determined by the shape of the spacer and the method of holding the planar separation membrane on the spacer, and examples thereof include a plate shape, a rod shape, and an inverted conical shape. Particularly, in the present invention, the plate-like shape is preferable, and the one having both surfaces formed of flat separation membranes is preferable.

The material of the planar separation membrane is not particularly limited as long as clear filtered water can be obtained, and known ultrafiltration membranes and microfiltration membranes can be used, and the membrane pore size can be appropriately selected according to the purpose. Good.

The total area of the planar separation membrane per one filter body is usually selected from the range of 4 to ²⁰ m ² . The filter is placed in the filtration device of the present invention, but the position of the placement is not particularly limited, but the bubbles and / or the water flow due to the bubbles from the air diffuser which is also provided in the filtration device are flat. It is preferable to arrange them so that they easily collide with the surface of the separation membrane. In particular, when a plurality of filter bodies are provided, the planar separation membrane surface of each filter body may be set to be parallel to the vertical direction and the spacing between the plane separation membranes may be appropriately set. At the same time, it is preferable to dispose the air diffuser on the lower side or the lower side of the filter body, for example, below the gap between the filter bodies.

The air diffuser used in the present invention is roughly composed of a blower, a pipe line, and an air diffuser, but a commonly known one can be applied, and its structure is not particularly limited, The air diffuser is generally tubular or plate-shaped.

The present invention maintains the cleanliness of the planar separation membrane by the diffused gas from the diffuser, but the method of supplying the diffused gas into the tank is not particularly limited, and the supply amount is not limited. The setting of supply time, stop time, etc. is appropriately selected according to the type of suspension, the type of filter body, the standard of filtered water, and the like.

In particular, the present invention has a feature that the cleanliness of the film surface can be maintained higher by intermittently setting the amount of diffused gas per unit time to be large. In this case, it is preferable that the larger set time zone (Gt) is shorter in time than the other time zones (Ct). The supply amount per unit time is Ct when Gt
Although it is set to be larger than time, it usually maintains a constant level with the lapse of time, but increase / decrease or supply stoppage may be allowed in each time zone. When a plurality of diffuser tubes are used, the supply specification may be set independently for each diffuser tube, or the diffuser tubes may be connected and set uniformly. The means for this setting is arbitrary, and may be automatic or manual, and examples thereof include control of the blower itself and a combination of the blower and a valve.

The type of gas to be diffused is appropriately selected depending on the properties of the suspension to which the present invention is applied. In the case of an aerobic biological treatment liquid, an oxygen-containing gas such as air is generally used and anaerobic gas is used. In the case of the sex organism treatment liquid, nitrogen gas can be used.
The suspension of these treatment liquids or the like may be introduced from the outside or treated in the apparatus of the present invention from the beginning. That is, it is obvious that the present invention has a function of treating sewage and the like in addition to the function of membrane separation.

Any filtration pressure generating means may be used as long as the filtration method applied to the present invention is a method of transferring filtered water from the outside of the planar separation membrane, that is, from the side in contact with the suspension to the inside of the membrane. it can. For example, it is possible to use a pump to make the inside of the filter a negative pressure, to seal the tank to make the inside of the tank a positive pressure, and to use a siphon.

The filtered water collecting mechanism when a plurality of filter bodies are provided may be carried out individually for each filter body or for connecting each filter body. For example, there may be mentioned a method in which a filtered water outflow pipe is provided in each spacer and the spacers are connected to each other for suction filtration with one pump.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation and one embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a tank in which an arbitrary suspension is stored, and 2 is an inflow portion of the suspension.

The membrane separation apparatus of the present invention is roughly composed of a tank 1, a flat membrane module 3 which is a filter, and an air diffuser 7. In the tank 1, a plurality of flat membrane modules 3 each having a planar UF or MF membrane 5 provided on both surfaces of a spacer 4 of a plate-shaped porous body as shown in FIG. , Soaked in parallel.

Outflow pipes 7 for membrane permeate are provided from the respective filtration modules 3. The outflow pipe 5 communicates with a membrane permeation water suction pump 8. An air diffuser 9 composed of an air diffuser or an air diffuser is provided below the flat membrane module 3, and air and other gases 10 are diffused by a blower 11. When anaerobic microorganisms such as methane-fermenting bacteria are subjected to membrane separation, a gas containing no oxygen such as nitrogen gas or methane gas is used as the gas 10.

In the present invention, the concept of intermittently increasing the discharge amount of the gas 10 is important, and it is possible to prevent the film contamination more effectively than when a fixed amount of gas is diffused.
It was experimentally confirmed that a high membrane flux can be secured for a long time.

The means for intermittently increasing the flow rate of the gas 10 is easy, and any means can be applied, but in the example of FIG. 1, a blower 13 is provided and the valve 12 is intermittently opened and closed. Is.

The reason why the contamination of the film can be effectively prevented by intermittently increasing the diffused flow rate of the gas 10 is not clear at present, but it can be inferred as follows.

That is, when the diffused flow rate of the gas 10 is increased intermittently, the flow pattern of the flow near the flat membrane changes drastically, and at that time, the contaminants on the membrane surface are removed and the membrane surface is kept clean. It seems that

The pattern of the magnitude of the gas flow rate can be variously changed, but the experimental results show that the method of increasing the gas flow rate in a short cycle is more effective than increasing the gas flow rate with a long interval. there were.

That is, for example, a cycle of increasing the time to 1 hr for 6 minutes is more effective than increasing the cycle to 5 hr for 30 minutes once. Further, the distance between the gaps 6 between the adjacent modules of the flat sheet membrane module 3 is an important factor, and if it is too wide, membrane contamination proceeds, and if it is too narrow, it is likely to be clogged with impurities. According to the experimental result, 10 to 30 mm was most suitable.

The installation method of the air diffuser 9 is also a very important factor. As shown in FIG. 2, the air diffuser 9 consisting of an air diffuser or a plate is provided in each gap 6 in the lateral direction of the flat sheet membrane module. The method of installation is the most preferable.

According to this method, each membrane surface of the flat sheet membrane module 3 can be surely given a turbulent water flow due to the rise of bubbles, and the membrane contamination can be effectively prevented. The types of flat membrane separation membranes used in the present invention include UF
Membrane (that is, ultrafiltration membrane), MF membrane (that is, microfiltration membrane)
Various types can be used and may be selected according to the type of reaction and the type of suspension.

For example, when applied to wastewater treatment and tap water treatment, an MF membrane having a pore size of about 0.01 to 1 μm is used, and for advanced treatment, a molecular weight cutoff is 1000 to 10 μm.
A UF film of about 0000 can be used.

Although the apparatus of the present invention is suitable for separating microbial suspensions, it is also suitable for injecting a flocculant such as aluminum sulfate into river water to separate produced flocs. Experimental Example A demonstration experiment of the performance of the present invention was conducted by using the present invention as an apparatus for treating activated sludge of sewage.

A water tank having a width of 30 cm, a length of 40 cm and a height of 70 cm was filled with MLSS3500 mg / l of activated sludge slurry (water level 50 cm), and two flat membrane modules described below were dipped vertically.

Flat membrane module specifications: Size: 15 × 15 cm square MF membrane Membrane pore size: 0.5 μm Spacer: Plastic porous body (plate-like) with pore size of 150 μm Increase or decrease in the next cycle.

100 liters air / min for 30 minutes, then 300 liters air / min for 3 minutes, then reduce to 100 liters air / min and repeat for 30 minutes.

When the operation was continued for 6 months under these conditions, the membrane permeation flux became like the line a in FIG. Membranes were never washed with chemicals during this experiment.

Also, the line b in the figure shows the diffused flow rate of the air quantity as 1
The results are shown in the case of performing at a constant rate of 00 liter / min. Apparently, the intermittent increase / decrease method of air is effective in keeping the flux high.

Further, since the membrane used in the filter body of the present invention is flat, no SS dents and sticking to the inside such as a hollow fiber membrane bundle module were observed at all, and it was maintenance-free. .

[0043]

EFFECT OF THE INVENTION SS on the membrane surface, such as the hollow fiber membrane method,
There is no sticking of sludge and fiber components, and maintenance-free operation is possible.

The permeation flux of the membrane can be stably maintained at a high value for a long period of time. Since the flat membrane is attached to the spacer and simply immersed in the tank, the device and production are simple and the production cost is low.

Even if the membrane contamination due to an unexpected trouble occurs and the permeation flux decreases, just lift the flat membrane module and spray it with high pressure water.
Easy to wash. In the hollow fiber membrane method, the hollow fibers cannot be washed without unraveling them one by one, so it cannot be carried out without manual labor, and it takes a lot of time and labor.

Since the film surface is flat, the water flow turbulence due to the bubbles can be surely given to each film surface.
It is impossible for the hollow fiber membranes to evenly disturb the surface of each hollow fiber membrane.

As a result, film contamination is extremely unlikely to occur.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a membrane separation device of the present invention.

FIG. 2 is a perspective view showing an example of a filter body used in the present invention.

FIG. 3 is a graph showing the results of an experimental example using the device of the present invention.

FIG. 4 is a diagram for explaining an example of a conventional membrane separation device.

[Explanation of symbols]

 1 Tank 2 Inflow Part 3 Flat Membrane Module 4 Spacer 5 Planar UF or MF Membrane 6 Gap 7 Outflow Pipe 8 Membrane Permeate Suction Pump 9 Diffuser 10 Gas 11 Blower 12 Valve 13 Blower 21 Aeration Tank 22 Hollow Fiber Membrane Module 23 Air diffuser 24 Air 25 Suction pump

Claims (1)

[Claims] 1. A filter body comprising a spacer and a planar separation membrane, one or more filter bodies provided therein, and a tank for receiving a suspension, and a lower portion of the filter body or a side portion below the filter body. And a means for setting the amount of diffused gas per unit time from the diffuser to be large intermittently.