KR20070022044A - Back washing method and system of filtration membrane - Google Patents

Abstract

The backwashing method is incorporated in a thin film filtration apparatus in which a ceramic filtration thin film comprising a substrate layer 11b having a myriad of filtration pores and a separation layer 11a having filtration pores smaller than this substrate layer is disposed in the casing. Air controlled by the pressure p1 is supplied to the secondary side of the filtration membrane, and the filtered water in the membrane filtration is gradually drained to the primary side. Thereafter, the air pressure rises to the pressure p3, and the contaminated substance is peeled off by extruding the filtered water in the filtration thin film together with the air to the primary side. Unlike the conventional case, since a large amount of backwash drains are never drained at the same time, the efficiency of backwashing is therefore not reduced, and the backwash drain pipe can be designed with a small diameter. As a result, the installation can be made compact, and the freedom of installation of the installation can be improved.

Backwash, filtration, thin film

Description

BACK WASHING METHOD AND SYSTEM OF FILTRATION MEMBRANE

The present invention relates to a backwashing method and a backwashing apparatus for a thin film.

As shown in FIG. 4, a thin film filtration device as illustrated in FIG. 2 includes a casing 13 having a thin film element 1 having a plurality of filtration flow paths 12 arranged in the porous portion 11 in parallel with each other. It has a structure arranged inside. The membrane filtration device performs the filtration as follows. In the cross flow filtration method, raw water a is introduced into the primary inlet side chamber 13a. The raw water is filtered by the fine filtration pores of the porous portion 11 while passing through the filtration flow path 12, and then in the form of the returned flow b, which is returned, the primary outlet side chamber 13b and the upper header tube ( Circulating through 17). Filtrate water is extracted from the header tube (14). In the Dead End Filtration method, after filling the primary side of the device with water, the valve located at the top of the casing is closed. The introduced raw water is treated through the filtrate header tube 14 to obtain the whole amount as the filtrate. Filtrate water (c) is extracted from the secondary chamber (13c) located between the side of the casing (13) and the side of the filter element (1).

As the filtration operation proceeds, separated suspended solids (SS) are deposited on the inner surface of the filtration channel 12 to form a polluting material, which causes a decrease in filtration efficiency. In this case, the filtration operation is stopped at an appropriate timing, and in the course of the back washing operation, the back washing water f is supplied from the secondary chamber 13c at a high pressure to flow back through the filtration pores of the porous portion 11. In addition, the contaminants blocking the inner surface of the filtration channel 12 are removed. Backwash water (f) is removed in the form of backwash wastewater (e) after removing contaminants.

In this case, filtrate (c) is generally used as backwash water (f). As the backwash operation is repeated, the amount of backwash wastewater e is increased while the amount of filtrate c is relatively reduced. As a result, the problem that the working efficiency of a filtration apparatus falls. In order to cope with this problem, a method of performing backwashing by supplying high pressure air instead of using filtrate (c) as backwashing water (f) has been proposed (see Patents 1 and 2).

However, even when backwashing using filtrate water and backwashing using high pressure air, a large amount of water present inside the thin film element 1 must be rapidly extruded toward the primary side at a time. The washing operation can be performed effectively. For this reason, it is necessary to design the diameter of a conveying pipe to a magnitude | size big enough so that the flow of backwash wastewater may be facilitated. However, this hinders the compactness of the thin film filtration plant and reduces the installation freedom of the plant. In actual equipment in which a plurality of devices are used as a single work unit, for example, as shown in FIG. 5, a transport pipe for improving the flow of backwash waste water is used as the lower header pipe 15, and the thin film device 1 is used. Directly with the lower part of the casing to accommodate the. In this structure, both the lower header pipe 15 and the drain valve 16 for the backwash wastewater need to have a large diameter in order to allow the backwash wastewater to flow quickly in a plurality of devices.

Patent Document 1: Japanese Patent Laid-Open No. 2002-2126468: Claim 1, Paragraph (0010)

Patent Document 2: Japanese Patent Laid-Open No. 2002-35748: Claim 2, Paragraph (0007)

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the conventional method described above, and its object is to design a smaller diameter of the backwash wastewater drain pipe without lowering the backwashing efficiency, thereby improving the compactness and freedom of the plant. The present invention provides a backwashing method and a backwashing device which can be improved.

In order to solve the above problems, the backwashing method of the filtration thin film of the present invention provides a pressure-controlled air to the secondary side of the filtration thin film clogged with contaminants, so that the retained filtrate in the thin film filtration device is supplied to the primary side of the filtration thin film. Gradually draining the water, and increasing the air pressure to extrude the water inside the filtration thin film together with the air to the primary side to separate the contaminants.

The thin film filtration device preferably comprises a ceramic filtration thin film comprising a substrate layer having a myriad of filtration pores, a separation layer having finer filtration pores than the substrate layer, and a casing having the ceramic filtration thin film disposed therein. do.

The present invention also gradually drains the filtered water remaining in the thin film filtration apparatus to the primary side, and thereafter, the residual water in the space extending from the surface of the substrate layer of the ceramic filtration thin film to the interface between the substrate layer and the separation layer to the primary side. It further comprises the step of extruding. In addition, the present invention can replace the washing water containing the cleaning chemical with the remaining water in the filter element prior to the backwash operation.

In addition, the backwashing method for a backwashing device used in the thin film filtration device of the present invention manufactured to solve the above problems includes a filtration element formed of a ceramic filtration thin film having a myriad of filtration pores, and the filtration element is disposed therein. It includes a casing, and is provided with a filtered water header tube on the lower side of the filtered water pipe serving as a backwash air supply pipe, and a backwash air source capable of controlling the pressure at the tip of the backwash air pipe. .

1 is a schematic configuration diagram of a thin film filtration device.

2 is a perspective view of a thin film filtration element.

Figure 3 is a schematic diagram showing the filtration of a thin film to show the backwashing method of the present invention.

4 is a block diagram of a conventional filtration device.

5 is a schematic diagram showing substantial conventional equipment equipped with a plurality of elements.

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described, referring FIGS. The thin film filtration apparatus to which the present invention is applied is basically the same as described above. That is, as shown in FIG. 2, the thin film filtration apparatus has the structure which arrange | positioned the thin film element 1 in the casing 2 in which the several filtering flow path 12 was provided in parallel in the porous part 11. As shown in FIG. The upper and lower outer peripheral portions of the thin film element 1 are sealed by the packing 2d, so that the upper and lower facing cross-sectional views of the thin film element 1 itself are also sealed. Due to this structure, raw water and filtered water never mix with each other. The raw water a is introduced into the primary inlet side chamber 2a, via the filtration flow path 12, and the primary outlet side chamber 2b and the upper header tube 24 in the form of the transfer raw water b. Filtration is carried out by a circulating Cross Flow Filtration method or a whole amount filtration method of closing the valve x provided at an intermediate position in the primary outlet side chamber 2b. The raw water a is formed by the separation layer formed on the inner surface of the filtration flow path 12 and having fine filtration pores. The filtrate (c) is extracted from the filtrate pipe (22) to the filtrate header tube (21) via the secondary side chamber (2c) located between the side of the casing (2) and the side of the filtering element (1).

In the present invention, when the filtration operation in the membrane filtration device, the filtration membrane is covered with contaminants, the backwashing operation is 1) supplying the pressure controlled air from the secondary side of the filtration membrane, 2) pressurization Draining the retained filtered water in the thin film filtration apparatus to the primary by air, and 3) increasing the air pressure to extrude the retained water in the filtered thin film with the air to the primary side to exfoliate the contaminants. . Prior to the backwashing operation, the remaining water in the thin film element may be replaced with the washing water containing the cleaning chemical.

This will be explained in more detail from now on. First, the filtration element 1 has a filtration thin film structure, and as shown in FIG. 3 (A), the filtration element 1 has a substrate layer having a myriad of ceramic coarse grains (1ly) and a myriad of filtration pores ( 11b), a ceramic fine grain 11x provided on the primary side (filtration flow path 12 side) of the substrate layer 11b, and a separation layer each having a filter pore having a size larger than that of the substrate layer 11b. 11a).

(Step 1)

In the present invention, the thin film filtration device in which the filtration element 1 is disposed in the casing 2 is backwashed, and as in step 1, as shown in Fig. 3A, the separation layer 11a, the substrate layer 11b, and Filtrate pipe 22 used as a drain and air pipe and a backwash air pipe in the secondary chamber 2c positioned between the filtering element 1 and the casing 2 while the secondary chamber 2c is filled with filtered water. Supply air (g) with pressure control

In step 1, air g having a pressure p1 lower than the foaming pressure of the substrate layer 11b is sent to the secondary chamber 2c. As a result, as shown in Fig. 3B, the inside of the secondary chamber 2c is replaced with air, and the filtered water is extruded to the primary side (i.e., the raw water side) and drained. By controlling this pressure p1, the retention filtration water in a thin film filtration apparatus can be gradually drained to a primary side.

(Step 2)

The present invention may also include the following step 2. That is, in step 2, the air g at the higher pressure p2 can be supplied by the step of extruding the filtered water in the secondary chamber by the air at the pressure p1. As a result, as shown in Fig. 3C, inside the substrate layer 11b (in the space extending from the surface of the substrate layer 11b to the interface between the substrate layer 11b and the separation layer 11a). The retained water can be replaced with air and gradually drained to the primary side.

In this case, the pressure p2 uses a pressure higher than the pressure p1 adopted in step 1. That is, the pressure p2 is set higher than the foaming pressure of the substrate layer 11b but lower than the foaming pressure of the separation layer 11a. In addition, by supplying the air at the pressure p2 of step 2 to step 1, it is also possible to substantially replace the secondary chamber 2c and the substrate layer 11b. Thus, step 2 may be performed after step 1 or steps 1 and 2 may be executed substantially simultaneously. Air with pressure p2 cannot pass through the separation layer.

(Step 3)

Through the two steps described above, after the replacement operation in the secondary chamber 2c and the substrate layer 11b by the pressurized air, in step 3, as shown in FIG. 3 (D), the separation layer 1la Air g having a pressure p3 above the foaming pressure is provided. As a result, the pressurized air extrudes the retained water in the separation layer 11a into the filtration flow path 12, and simultaneously blows off the air in the form of gushing to exfoliate the deposited material. In this way, clogging of the filtration thin film is eliminated. Residual water in the filtration membrane that is extruded into the filtration channel 12 in step 3 accounts for about 2.5% of the casing volume (see below). Therefore, even if the diameter of the lower header pipe 25 through which the backwash drainage is not expanded, it is possible to drain at a high flow rate.

Depending on the type of thin film contaminant, it may be necessary to extrude the contaminant by the force of backwash water. In this case, water of about 24% of the volume of the casing 2 (that is, the volume of water remaining in the substrate layer 11b and the separation layer 11a, see below) by the direct transition from step 1 to step 3. By extruding from the separation layer 11a at high speed, the thin film can be washed effectively.

Next, the backwashing apparatus of the present invention will be described.

As shown in FIG. 4, the filtrate header tube 14 was conventionally installed above the filtrate pipe 15 which also serves as a backwash air supply pipe. In particular, since water pressure is used during backwashing, when air remains in the flow path, the backwashing air pressure is lost due to the compression of the residual air, causing a significant decrease in backwashing efficiency. In order to prevent this, it is necessary to exhaust the air in the filtrate water pipe 15 by providing the filtrate header pipe 14 on the filtrate water pipe 15.

In contrast, in the backwashing apparatus of the present invention, the filtrate header tube 21 shown in FIG. 1 is provided on the lower side of the filtrate pipe 22 which also serves as the backwashing air supply pipe. In the conventional structure, the retention filtrate in the filtrate header tube 14 flows in response to the countercurrent flow during backwashing. Alternatively, the present invention includes the step of replacing the water in the filtered water supply pipe with air prior to the backwash operation. Thus, the presence of residual air does not affect the backwash effect. For this reason, it becomes possible to provide the filtrate header tube 21 downward. As a result, even if air g is supplied from the backwashing air source 23, the filtered water in the filtrate header tube 21 never flows back, thereby reducing the amount of backwashing drainage.

Example

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described.

When the thin film element 1 having 2000 filtration flow paths having a diameter of 180 mm and a length of 1000 mm and each having an internal diameter of 2.5 mm is disposed in a casing 2 having a diameter of 200 mm, the volume of the casing (inlet chamber and outlet chamber) Is 100%, the volume of the secondary chamber 2c is 21%, the volume of the filtration element is 48%, and the volume of the filtration flow path is 31%. Also, in the filtration thin film element 1, when the ratio of water to the substrate layer and the separation layer is 9 to 1 and the porosity of the substrate layer and the separation layer is 50%, the volume of the filtered water remaining in the substrate layer and the separation layer is 21, respectively. %, 2.5%.

In the conventional backwashing method, 21% of the volume of the water in the secondary chamber in the casing, 21% of the substrate layer, and 44.5% of the total volume of 2.5% of the separating layer are discharged as at least backwash drainage, and the above-described thin film is reversed. When washing, drain up to 40 liters of water at a maximum flow rate of 2 m / s. Alternatively, in the present invention as described above, only 1 L of water may be sufficient to flow in the method described in step 3. Even in the method of directly performing the above-described steps 1 to 3, only 6 L of water is sufficient to flow. In this case, in the case of flowing at the same flow rate as described above, a pipe of 80 mm diameter is conventionally required to flow 40 L of water, but in the present invention, since only 1 L of water is drained, a pipe of 25 mm diameter is sufficient. 50mm diameter pipe is enough to drain 6L of water. The diameter adopted depends on the water quality or the working conditions, but in any case can be significantly compacted compared to the prior art.

The thin film used in the examples includes a substrate layer having a pore diameter of about 10 μm and a separation layer having a pore diameter of 1 μm. When the pressure p1 is set to 10 kPa, the pressure p2 is set to 50 kPa, and the pressure p3 is set to 30OkPa, it is possible to successfully perform the backwashing performed in accordance with the above three steps.

According to the present invention, the air whose pressure is controlled is supplied from the secondary side of the filtration membrane covered with contaminants, and the retained water and air remaining in the filtration membrane are replaced. As a result, the retained filtrate in the thin film filtration device is gradually drained to the first order side. In such a structure, the backwash water can be drained without expanding the diameter of the pipe flowing backwash drainage. Thereafter, the air pressure is increased, and the water inside the filtration thin film is extruded together with the air to the primary side to remove contaminants. Since the amount of backwash wastewater used at this time is relatively small, the wastewater can be drained even if the diameter of the pipe through which the backwash wastewater flows is not increased. Therefore, the equipment such as the lower header pipe can be designed to have a smaller diameter without reducing the backwashing effect, thereby making it possible to compact the equipment and improve the freedom of installation of the equipment.

The backwashing apparatus of the present invention also serves as a backwashing air supply pipe and arranges the filtrate header tube on the lower side of the filtrate pipe. For this reason, not only the backwashing operation of the present invention described above can be performed, but also the filtrate in the filtrate header tube does not flow back when the backwashing air is supplied. As a result, there is an advantage that the backwash drainage decreases, so that the recovery rate represented by the ratio of the amount of drainage at the time of backwashing to the amount of filtered water is improved.

Claims (5)

Supplying pressure-controlled air to the secondary side of the filtration membrane clogged with fouling material, gradually draining the retained filtrate in the membrane filtration apparatus to the primary side of the filtration membrane, and Increasing the air pressure and extruding contaminants by extruding water inside the filtration membrane together with air to the primary side; Thin film backwashing method comprising a. The method of claim 1, The thin film filtration device A ceramic filtration thin film comprising a substrate layer having a myriad of filtration pores, and a separation layer having filtration pores finer than the substrate layer, and And a casing having the ceramic filtration thin film disposed therein. The method of claim 2, After gradually draining the retention filtration water in the thin film filtration apparatus to the primary side, the retention water in the space extending from the surface of the substrate layer of the ceramic filtration thin film to the interface between the substrate layer and the separation layer of the ceramic filtration thin film to the primary side. Pushing out the steps Thin film backwashing method further comprising. The method of claim 1 A thin film backwashing method, wherein the remaining water in the filtration element is replaced with a washing water containing a cleaning chemical prior to the backwashing operation. In the backwashing device for thin film filtration apparatus which consists of a filtering element formed from the ceramic filtration thin film which has a myriad of filtration pores, and the casing in which this filtration element is arrange | positioned, A backwashing device comprising a backwashing air supply source capable of controlling pressure at a tip of a backwashing air supply pipe, and a filtrate header pipe disposed on a lower side of the filtrate pipe serving as a backwashing air supply pipe.

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