JPH11267471A - Membrane filter device and operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable efficient water treatment for a long period by providing a membrane filter device using a filter membrane module for removing the pollutants in raw water for treatment with a water quality inspection apparatus and actuating a washing mechanism for washing a filter membrane when the water quality of a permeate exceeds a predetermined value. SOLUTION: The raw water is sent from a raw water supply port 9 through a raw water tank 2, a raw water supply pump 3 and a raw water supply valve 7 to the filter membrane module 1. The permeated water after the filtration is taken out of a permeated water intake port 10 through a permeated water line 11. During the filtration operation, the permeated water quality is inspected by the water quality inspection apparatus 4. When the prescribed water quality is exceeded, the raw water supply valve 7 is closed and thereafter, an air supply valve 15 and an air discharge valve 16 are opened to execute air bubbling washing. The air supply valve 15 and the air discharge valve 16 are closed after washing and the raw water supply valve 7 is opened to restart filtration operation. The water quality inspection apparatus to be used 4 includes a turbidity meter for measuring the pollutant concn. in the water, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane filtration device using a filtration membrane module and a method of operating the membrane filtration device, and more particularly, to a membrane filtration device for purifying water using a filtration membrane module. And an operation method of the membrane filtration device.

[0002]

2. Description of the Related Art Recently, a membrane filtration system using a filtration membrane module is being used in a wide variety of water treatment fields from drinking water production to sewage and wastewater treatment. The membrane filtration system is very compact compared to the conventional sand filtration method and coagulation sedimentation method, and the obtained water quality is very high. It is expected to carry. Various required characteristics, such as water permeability, pressure resistance, heat resistance, and stain resistance, depending on the quality of the raw water to be treated and the type of equipment, also exist as filter membrane modules. Is being done.

[0003] Generally, a filtration membrane module can obtain high water quality with less turbidity as compared with techniques other than membrane filtration, and can also treat bacteria and microorganisms by chlorination. Regarding the water quality of (water), it has been often developed with the aim of obtaining a module and an apparatus that can be maintained with as high an amount of water as possible, that is, as high as possible. Therefore, the main purpose of the operation method of the membrane filtration device is to maintain water permeability. Specifically, since the membrane is clogged with turbidity and the water permeability is reduced, a method of recovering the water permeability of the membrane by regularly cleaning the membrane is often adopted.

[0004]

However, recently,
The generation of carcinogenic substances such as trihalomethane by chlorination has been considered a problem, and the problem of pathogens such as Cryptosporidium, which is resistant to chlorine, has arisen, making it impossible to rely on chlorination. For this reason, recently, the water quality required for the filtration membrane module has also become very high.

[0005] Many filtration membrane modules are made of organic polymers, and in water treatment, the pores in the filtration part are several microns to sub-micron in size. However, the pores of the filtration membrane have a distribution, and not all pores have the same size. As a result, in the initial stage of filtration, high water quality can be maintained, but if pressure is applied to the filtration membrane for a long time, turbidity in raw water may leak from relatively large pores. Was found as a result of the study by the present inventors. This degree is not uniform because it varies depending on the characteristics of the membrane, the quality of the raw water to be treated, the operating pressure, and the like. In particular, filtration membrane modules are often operated to obtain a fixed amount of permeate. Specifically, a method is adopted in which the filtration pressure is increased in response to a decrease in water permeability due to clogging of the membrane, but as a result of a study by the present inventors, the pressure is constant. As compared with the case, it was confirmed that the higher the pressure was, the more easily the turbidity leaked.

[0006] Therefore, the conventional periodic cleaning of the membrane cannot respond to the leakage of turbidity, so that it is necessary to shorten the cleaning interval in order to maintain high water quality above a certain standard. . However, the short cleaning interval
The substantial operation time for filtration is short, that is, the amount of permeated water is reduced, and the wasteful cost required for washing is increased.

An object of the present invention is to provide a membrane filtration device using a filtration membrane module having high water quality and capable of efficient water treatment and a method of operating the membrane filtration device.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a membrane filtration device using a filtration membrane module for removing turbidity in raw water by generating a pressure difference on the membrane surface of the filtration membrane. Basically achieved by a membrane filtration device that is equipped with a water quality inspection device that automatically performs inspection and a cleaning mechanism that cleans the filtration membrane when the water quality of the permeate exceeds a predetermined value. Is done.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, the quality of permeated water is monitored, and when the water quality is reduced, the filtration process is interrupted and the washing is performed to obtain high-quality water and to maximize the operation time for filtration. Therefore, the performance of the filtration membrane module can be sufficiently exhibited.

FIGS. 1 and 2 show examples of application of the present invention. FIG.
Is a membrane filtration device provided with a circulation type water quality inspection device 4 in a permeated water container. Raw water is sent from the raw water supply port 9 to the filtration membrane module 1 through the raw water tank 2, the raw water supply pump 3, and the raw water supply valve 7. Also, the permeated water is
It is taken out from the permeated water intake 10 through the permeated water line 11. During the filtration operation, the quality of the permeated water is inspected by the water quality inspection device 4, and when the water quality exceeds a predetermined level, the raw water supply valve 7 is closed, the air supply valve 15 and the air discharge valve 16 are opened, and air bubbling is performed. It is designed to perform cleaning. After the washing, the air supply valve 15 and the air discharge valve 16 are closed, the raw water supply valve 7 is opened, and the filtration operation is restarted.

FIG. 2 shows a membrane filtration device provided with a water quality inspection device 4 capable of constantly monitoring permeated water online. The operation is the same as that of the device shown in FIG. The direct measurement has the advantage that the response of the permeated water quality change is fast.

Here, the water quality inspection apparatus to be used is not particularly limited as long as it can measure turbidity of permeated water and has an alarm output when a set value is exceeded. Specifically, a turbidity meter for measuring the turbidity concentration in water, an electric conductivity meter, or the like can be used. For example, there is a type that has a mechanism that periodically measures water quality data using a timer and feeds back the result as an alarm output to the pressure sensor 6 and the raw water supply valve 7 with an electric signal. An inspection device that can quickly feed back the results is preferable.

[0013] The filtration membrane used in the present invention is not particularly limited as long as it can remove turbidity in the raw water to be treated. Examples of the shape include a flat membrane and a tubular membrane. It is not limited. As the above-mentioned tubular membrane, a hollow fiber membrane having a tube diameter of 1 mm or less to a capillary membrane of several millimeters or a tubular membrane of 1 cm or more can be applied.

For the purpose of the present invention, the size of the pores of the membrane is suitably a separation membrane of several nm to several μm, but is not particularly limited.

Although there is no particular limitation on the material of the film,
A porous membrane made of polyacrylonitrile, polyimide, polyether sulfone, polyphenylene sulfide sulfone, polytetrafluoroethylene, polypropylene, polyethylene, or the like is preferable for application of the present invention.

As for the shape of the module, in the case of a flat membrane,
Plate-and-frame type, spiral type, pleated type, rotating disk type, etc. are listed. In the case of tubular membrane, there are I-type in which hollow fiber membrane is arranged in an I-shape in a module container, and U-shape in which a hollow fiber membrane is arranged in a U-shape. Although it is mentioned, it is not particularly limited.

The method of washing the separation membrane module is not limited as long as the water permeability of the separation membrane module = filtration performance can be recovered. Typically, washing with pure water, from the permeate side to the raw water side Back-pressure washing for back-filtration of permeated water, pure water, chemicals, etc., Aeration washing for removing airborne substances by sending bubbles to the separation membrane surface, Acid / alkali /
There is a method of washing with a chemical solution immersed in a chemical solution such as a detergent, and there is a method of selecting one of these methods, performing the method simultaneously in combination, or performing the method sequentially. As a cleaning method applied to the present invention, back pressure cleaning and diffused cleaning are most preferable because they are simple, have high cleaning effects, and are easy to carry out in combination.

[0018]

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited by this.

EXAMPLE As shown in FIG. 1, a hollow fiber membrane module 1 (manufactured by Toray Co., Ltd., manufactured by Toray Industries, Inc.) packed with 10,000 hollow fiber bundles of polyacrylonitrile porous hollow fiber membranes having an outer diameter of 450 μm and an inner diameter of 350 μm.
-20), using a centrifugal pump (CH2-30, manufactured by Grundfos) as the raw water supply pump 3,
As a low-concentration precision laser turbidimeter (MIKUNIKIKAI, MI
LPA-TM) was connected to the permeate line 11. When the turbidity of the turbidity meter 4 exceeds the set value, the raw water supply valve 7 is automatically closed by an alarm output from the turbidity meter, the supply of the raw water is stopped, and the air is supplied from the air diffuser 13 for a predetermined time. After performing the air diffusion and the swinging of the hollow fiber membrane, a separation membrane module device having a washing mechanism for draining was manufactured.

Using this apparatus, a quantitative filtration operation was performed on river water having a turbidity of about 10 ppm as a raw water at a permeated water amount of 0.5 m ³ / h. Here, the washing conditions are such that when the turbidity of the permeated water becomes 0.2 ppm or more, the amount of diffused air is 30 liters / liter.
It was set to perform aeration washing for 1 minute in 1 minute. At this time, the filtration stop time including the supply and drainage was 3 minutes. FIG. 4 shows the change over time in the quality of the permeated water. The permeate water turbidity of this example shown by the solid line is lower than that of the comparative example shown by the broken line.
That is, an operation result with good permeated water quality could be obtained.

Comparative Example As shown in FIG. 3, a filtration operation was performed under the same conditions as in the example using the same filtration membrane module device as in the example except that the operation of the cleaning mechanism was performed by the timer 14. Here, the washing conditions were set so that the air diffusion washing was performed under the same conditions as in the examples every 12 hours of the filtration operation. As a result, FIG.
As shown in the figure, the permeated water turbidity of the comparative example shown by the broken line was higher than that of the example shown by the solid line, that is, the permeated water quality was very poor.

[0022]

According to the present invention, the water quality of a permeated liquid is automatically inspected in a membrane filtration device using a filtration membrane module for removing a turbid substance in treated raw water by generating a pressure difference on the membrane surface of the filtration membrane. The membrane filtration device, which is equipped with a mechanism for washing the filtration membrane when the water quality of the permeate exceeds a predetermined value, enables high water quality and efficient water treatment. Was.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an example of a filtration membrane module device according to the present invention.

FIG. 2 is a circuit diagram of another example of the filtration membrane module device according to the present invention.

FIG. 3 is a circuit diagram of a filtration membrane module device used in a comparative example.

FIG. 4 is a diagram showing a temporal change in permeated water quality in an example and a comparative example according to the present invention.

[Explanation of symbols]

Claims (4)

[Claims] In a membrane filtration apparatus using a filtration membrane module for removing turbidity in raw water by creating a pressure difference on the membrane surface of a filtration membrane, a water quality inspection apparatus for automatically inspecting the quality of permeated liquid. And a washing mechanism for washing the filtration membrane when the water quality of the permeate exceeds a predetermined value. 2. The membrane filtration device according to claim 1, wherein the water quality inspection device is provided in the permeated water channel, and the water quality inspection device is a turbidity meter. 3. A cleaning mechanism for a filtration membrane comprising at least one of aeration cleaning to a raw water side, back pressure cleaning from a permeation side, and chemical cleaning. Membrane filtration equipment. 4. A method for operating a membrane filtration device using a filtration membrane module for removing turbidity in raw water by generating a pressure difference on the membrane surface of the filtration membrane, wherein the water quality of the permeated liquid is automatically adjusted. A method for operating a membrane filtration device, comprising: performing an inspection and washing a filtration membrane when a water quality of a permeate exceeds a predetermined value.