JPH04265128A - Membrane separation equipment - Google Patents

Abstract

PURPOSE:To maintain filter resistance low for a long time and to provide a maintenance-free membrane separation equipment. CONSTITUTION:The objective equipment consists of flat membrane modules 3 each of which is a filter medium consisting of a spacer 4 and a UF or MF membrane 5 (a planar separation membrane), a vessel 1 which is equipped with one or more flat membrane modules 3 and receives suspension liquid, and diffusing parts 9 of a diffuser arranged at the lower part of the flat membrane module 3 or at the lower side part of the filter medium. When the quantity of diffused air per hour from the diffuser is intermittently set large by a blower 11, a blower 13 and a valve 12, the movement of the suspension liquid is generated by gas 10, thus capable of maintaining the cleanness of the membrane surface.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to various arbitrary suspensions (
For example, suspensions of microbial particles, inorganic particles, etc.)
The present invention relates to a membrane separation device that easily and efficiently performs membrane separation to obtain a clear separated liquid.

0002

2. Description of the Related Art Conventionally, an apparatus is known in which a bundle-like module of hollow fiber membranes is immersed in an aeration tank to obtain a permeated liquid (see FIG. 4).

In the apparatus shown in FIG. 4, a hollow fiber membrane module 22 is immersed in an aeration tank 21, and air 24 is supplied from an aeration pipe 23.
The suction pump 2 maintains the inside of the tank aerobically to ensure the growth of microorganisms and maintain the filtration function of the hollow fiber membrane.
5, the permeated water 26 of the suspension in the tank that has been treated with microorganisms is obtained from the hollow fiber membrane.

However, when the present inventor conducted a follow-up test on this prior art, the following serious drawbacks were found:
It turned out to be impractical. That is, the apparatus shown in FIG. 4 has the following problem.

[0005] SS particles such as activated sludge and fibers enter the inside of the bundle of hollow fiber membranes and become attached or fixed, resulting in a rapid increase in filtration resistance. ■ It is extremely difficult to wash and remove the SS that has entered the inside of the hollow fiber membrane bundle.
Adhering sludge and fibers cannot be removed by removing the hollow fiber membrane module and spraying it with high-pressure water while loosening the fibers. This requires a lot of effort and is practically impossible to perform.

[0006]

[Problems to be Solved by the Invention] It is an object of the present invention to completely solve the serious drawbacks of the above-mentioned conventional devices, and to provide a new technology that can maintain low filtration resistance for a long period of time and is maintenance-free. That is the issue.

[0007]

[Means for Solving the Problems] The present invention was completed after conducting various studies in order to solve the drawbacks of the prior art, and it was discovered that the drawbacks of the prior art could be solved by the following means.

That is, the present invention provides a filter consisting of a spacer and a planar separation membrane, a tank in which one or more of the filters are arranged and receives a suspension, and a lower part of the filter or a lower side of the filter. 1. A membrane separation device comprising a diffuser having a diffuser section disposed on one side, and comprising means for intermittently setting a large amount of diffused gas per unit time from the diffuser. It is.

The novel idea of the present invention is as follows. ■
Instead of using hollow fiber membranes, we use a filter body with a planar separation membrane, which makes it impossible for SS to get stuck inside the bundle.

[0010] Conventionally, it has been known to install a planar separation membrane in a structure such as a filter press or a dehydrator, but there has been no concept of immersing it in an aeration tank using the method of the present invention. Ta.

(2) It has been found that membrane contamination can be effectively prevented by intermittently increasing or decreasing the amount of air diffused to create disturbances on the membrane surface. The filter body used in the present invention has a filtration section composed of at least a spacer and a planar separation membrane. The structure of the filter body has the function of filtering the suspension at least on the outside of the planar separation membrane and transferring the filtered water to the inside of the membrane, and further includes a means for taking out the transferred filtered water. As long as it is provided, there are no particular restrictions on the configuration of the filtration section. However, the external shape of the filtration part is preferably such that when the filter body is placed in the tank, the entire surface of the planar separation membrane can easily come into contact with the air bubbles supplied from the air diffuser and the water flow caused by the air bubbles.

[0012] The outer surface of the filtration section is formed of a planar separation membrane, but it is not necessarily necessary to form the entire outer surface with a planar separation membrane. can be formed.

Further, the shape of the outer surface of the planar separation membrane is not particularly limited as long as it satisfies the above conditions, and is not limited to only a flat surface, but can include any curved surface. The structure of the spacer is arbitrary and is not particularly limited as long as it supports the planar separation membrane and at least has the function of securing a space for allowing the filtrate to migrate into the interior. Further, it may be provided with a means for taking out the transferred filtered water to the outside, for example, an outflow pipe.

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

Adhesives, bolts and nuts, magnets, etc. can be used as means for supporting the planar separation membrane on the spacer. Therefore, the external shape of the filtration part of the filter body is determined by the shape of the spacer and the method of holding the planar separation membrane to the spacer, and is therefore arbitrary. Examples include a plate shape, a rod shape, and an inverted conical shape. In particular, in the present invention, a plate shape is preferable, and one in which both surfaces are formed of planar 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 precision filtration membranes can be used, and the membrane pore diameter can be appropriately selected according to the purpose. good.

[0017] The total area of the planar separation membrane per one filter body is usually selected from the range of 4 to 20 m2. The filter body is installed in the filtration device of the present invention, but its placement position is not particularly limited. It is preferable to arrange it so that it can easily collide with the surface of the separation membrane. In particular, when multiple filters are installed, it is important to ensure that the surfaces of the planar separation membranes of each filter are parallel to the vertical direction and that the spacing between the planar separation membranes is set appropriately. Preferably, at the same time, the air diffuser is disposed below or to the lower side of the filter, for example at the bottom of each filter gap.

The air diffuser used in the present invention is generally composed of a blower, a pipe, and an air diffuser, but commonly used and known devices can be applied, and there are no particular restrictions on the structure. The diffuser generally has a tubular shape, a plate shape, etc.

Although the present invention maintains the cleanliness of the planar separation membrane using the diffused gas from the diffuser, there is no particular restriction on the method of supplying the diffused gas into the tank, and the amount of supply , supply time, stop time, etc. are appropriately selected depending on the type of suspension, the type of filter, the standard of filtrate, etc.

In particular, the present invention has a feature that the cleanliness of the membrane surface can be maintained at a higher level by intermittently setting a large amount of diffused gas per unit time. In this case, it is preferable that the large time period (Gt) be set shorter than the other time periods (Ct). The supply amount per unit time is Ct when Gt is used.
Generally, each level is set to be higher than the other times, but each level is normally maintained at a constant level over time, but an increase/decrease or supply stoppage may be allowed in each time period. When a plurality of air diffusers are used, the supply specifications may be set independently for each air diffuser, or may be set uniformly by connecting the air diffusers. This setting means is arbitrary and may be automatic or manual, and includes, for example, control of the blower itself, a combination of the blower and a valve, and the like.

[0021] The type of aeration gas 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; In the case of a biological treatment liquid, nitrogen gas may be used. These suspensions such as processing liquids may be introduced from outside or may be processed in the apparatus of the present invention from the beginning. That is, it is clear that the present invention has a function of treating sewage and the like in addition to the membrane separation function.

[0022] The filtration method applied to the present invention can use any filtration pressure generating means as long as it is a method of transferring filtrate water from the outside of the planar separation membrane, that is, the side that contacts the suspension to the inside of the membrane. can. Examples include creating a negative pressure inside the filter body with a pump, creating a positive pressure inside the tank by sealing the tank, and using a siphon.

When a plurality of filter bodies are provided, the filtrate water collecting mechanism may be implemented by each filter body individually or by connecting the filter bodies. For example, each spacer is provided with a filtered water outflow pipe,
An example of this method is to connect these and perform suction filtration using one pump.

[0024]

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

The membrane separation apparatus of the present invention is generally composed of a tank 1, a flat membrane module 3 which is a filter, and an aeration device 7. In the tank 1, a plurality of flat membrane modules 3 each having a planar UF or MF membrane 5 on both sides of a plate-shaped porous spacer 4 as shown in FIG. , installed in a parallel manner.

Each filtration module 3 is provided with an outflow pipe 7 for membrane permeated water. The outflow pipe 5 communicates with a membrane permeate water suction pump 8 . A diffuser section 9 consisting of a diffuser tube or a diffuser plate is provided at the bottom of the flat membrane module 3, and air or other gases 10 are diffused by a blower 11. When membrane-separating anaerobic microorganisms such as methane-fermenting bacteria, a gas that does not contain 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 gas 10 is important, and membrane contamination can be prevented more effectively than when a constant amount of gas is diffused.
It has been experimentally confirmed that high membrane flux can be maintained for a long time.

The means for intermittently increasing the flow rate of the gas 10 is easy and any means can be applied; however, in the example shown in FIG. It is.

Although the details of the mechanism as to why membrane contamination can be effectively prevented by intermittently increasing the gas 10 diffused flow rate are currently unknown, it can be inferred as follows.

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

Although the pattern of the gas flow rate can be changed in various ways, experimental results show that increasing the gas flow rate in short cycles is more effective than increasing the gas flow rate over a long period of time. there were.

That is, for example, it is more effective to increase the cycle time by 6 minutes every 1 hour than to increase the cycle time by 30 minutes every 5 hours. Further, the distance between the gaps 6 between adjacent modules in the flat membrane module 3 is an important factor; if it is too wide, membrane contamination will progress, and if it is too narrow, it will be easily blocked by foreign matter. According to experimental results, 10 to 30 mm was most suitable.

The installation method of the air diffuser 9 is also a very important factor, and as shown in FIG. The installation method is the most preferred.

[0034] According to this method, it is possible to reliably apply strong turbulence to the water flow due to the rise of air bubbles to the surface of each membrane of the flat membrane module 3, and it is possible to effectively prevent membrane contamination. The types of flat membrane separation membranes used in the present invention include UF
membrane (i.e. ultrafiltration membrane), MF membrane (i.e. microfiltration membrane)
Various types can be used, and the selection may be made depending on the type of reaction and the type of suspension.

For example, when applied to wastewater treatment and water treatment, MF membranes with a pore size of about 0.01 to 1 μm are used, and when performing advanced treatments, MF membranes with a molecular weight cutoff of 1000 to 10 are used.
A UF membrane of about 0,000 can be used.

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

A water tank measuring 30 cm wide, 40 cm long, and 70 cm high was filled with activated sludge slurry containing MLSS of 3500 mg/l (water level 50 cm), and two flat membrane modules described below were vertically immersed therein.

Flat membrane module specifications: Size: 15 x 15 cm square MF membrane Membrane pore diameter: 0.
5μm Spacer: Plastic porous body (plate-like) with pore diameter of 150μm Diffusing air amount: Increase or decrease the amount of air discharged from the diffuser pipe in the next cycle.

100 liters of air/min for 30 minutes, then
Repeat the cycle at 300 liters of air/min for 3 minutes, then reduce to 100 liters of air/min for 30 minutes.

When the operation was continued under these conditions for 6 months, the membrane permeation flux became as shown by line a in FIG. 3. During this experiment, the membrane was never cleaned with chemicals.

[0041] Line b in the figure indicates that the aeration flow rate of the air amount is 1.
The results are shown when the test was carried out at a constant rate of 00 liters/minute. Clearly, intermittent increases and decreases of air are effective in keeping flux high.

[0042] Furthermore, since the membrane used in the filter body of the present invention is planar, no SS was observed to be stuck inside the hollow fiber membrane bundle module, 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 or fibers, and maintenance-free operation is possible.

(2) 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 simply attached to a spacer and immersed in a tank, the equipment and manufacturing are simple and the manufacturing cost is low.

[0045] Even in the unlikely event that membrane contamination occurs due to unpredictable trouble and the permeation flux decreases, it can be easily cleaned by simply lifting the flat membrane module and spraying it with high-pressure water. In the hollow fiber membrane method, the hollow fibers cannot be cleaned unless they are loosened one by one, so it can only be carried out manually and requires a lot of effort.

(2) Since the membrane surface is flat, the turbulence of water flow caused by air bubbles can be reliably applied to each membrane surface. With hollow fiber membranes, it is impossible to uniformly disorder the surface of each hollow fiber membrane.

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

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an example of a membrane separation apparatus 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 apparatus 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 section 3 Flat membrane module 4 Spacer 5 Planar UF or MF membrane 6 Gap 7 Outflow pipe 8 Membrane permeate water suction pump 9 Aeration section 10 Gas 11 Blower 12 Valve 13 Blower 21 Aeration tank 22 Hollow fiber membrane module 23　Air diffuser pipe 24 Air 25 Suction pump

Claims (1)

[Claims] Claim 1: A filter consisting of a spacer and a planar separation membrane, a tank in which one or more of the filters are arranged and for receiving a suspension, and a tank disposed below the filter or on the side of the lower part of the filter. 1. A membrane separator comprising: an aeration device having an aeration section having a diffuser structure, and comprising means for intermittently setting a large amount of diffused gas per unit time from the aeration device.