KR100503783B1 - Two-way alternate backwashing method and equipment of hollow-fiber membrane module, and drinking water treatment equipment using the same - Google Patents

Abstract

The present invention includes a first opening and closing means for discharging the backwash water at both ends of the hollow fiber membrane module, the second opening and closing means for a predetermined time to open the first opening and closing means of the hollow fiber membrane Discharging the backwash water passing through the pores to the outside of the membrane module through the first opening and closing means (1); And closing the first opening and closing means for a predetermined time and opening the second opening and closing means to discharge the backwash water passing through the hollow fiber membrane pores to the outside of the separation membrane module through the second opening and closing means. It provides a method of backwashing a hollow fiber membrane module, characterized in that.

In addition, the present invention is a hollow fiber membrane module; A backwash feed water storage tank for storing the backwash water of the hollow fiber membrane module; A backwash pressurized pump connected between the backwash feed water storage tank and the hollow fiber membrane module to supply backwash water from the backwash feed water storage tank to the hollow fiber membrane module; Backwash water discharge pipes connected to both ends of the hollow fiber membrane module; First and second automatic valves respectively mounted to the discharge pipe; And an automatic valve control device for alternately opening the first automatic valve and the second automatic valve in order.

In addition, the present invention provides a hollow fiber membrane water treatment device comprising the backwashing device.

According to the present invention, it is possible to perform uniform backwashing of the hollow fiber membranes by differentially allocating the backwashing direction priority order and the backwashing time in each direction according to the inflow direction and the water quality of the raw water. Backwashing can be performed.

Description

TWO-WAY ALTERNATE BACKWASHING METHOD AND EQUIPMENT OF HOLLOW-FIBER MEMBRANE MODULE, AND DRINKING WATER TREATMENT EQUIPMENT USING THE SAME}

The present invention relates to a bidirectional cross backwash method of a hollow-fiber membrane module, a bidirectional cross backwash device and a water treatment apparatus using the same, and more specifically, to a direction of backwash water discharge of a hollow fiber membrane module. The present invention relates to a method for backwashing, a backwashing device and a purified water treatment device by sequentially crossing in the longitudinal direction of the hollow fiber membrane.

The separator is a tool for separating a substance according to the size of the molecule or the repulsive force between the molecule and the separator, and the driving force of the separation is pressure, concentration, and potential difference. When the membrane is used in the separation process, it is easy to automate and does not involve phase change and high temperature treatment. Therefore, it is being researched and used as a technology that can replace the separation processes of environmental pollution prevention facilities or the chemical industry. . Types of separation membranes include reverse osmosis membranes, nanofiltration membranes, ultrafiltration membranes, microfiltration membranes, ion exchange membranes, gas separation membranes, and pervaporation membranes. There are various types of membrane modules, such as plate-frame type, tubular type, spiral-wound type, hollow-fiber type and the like. Among these, the hollow fiber membrane module is a bundle of hollow fiber membranes having a skin layer of the membrane inside or outside the thin tube that can support the membrane itself. out), the surface layer on the outside of the tube is called an outside-in hollow fiber membrane. The diameter of the tube is generally about 0.2 ~ 1.5mm. Hundreds or thousands of hollow fiber membranes are arranged in the form of shells or tubes, depending on the size of the module and the diameter of the support, where the flow in the module has a laminar flow characteristic unlike the tubular case.

The filtration principle of the hollow fiber membrane module is that in the case of pressure-resistant type, water flowing into the inside of the hollow fiber is pressurized and discharged to the outside of the hollow fiber while penetrating the separator. As it penetrates, it is collected to be discharged inside the hollow fiber.

The performance of the membrane is degraded by membrane fouling phenomenon in which particulate or dissolved substances adhere to the membrane surface or the pore surface. To prevent such membrane fouling, the membrane's filtration performance should be restored by backwashing such as periodically washing the surface of the membrane during the membrane filtration operation or passing the washing water in the opposite direction of the filtration direction through the membrane pores. . The backwashing feed water is a mixture of filtered water or a washing agent such as an acid, an alkali or an inorganic and an organic detergent, and the backwashing feed water is pressurized by a backwash pump to perform backwashing.

In backwashing of the hollow fiber membrane module, the backwash water supply water is pressurized in the case of internal pressure type, flows through the pores from the outside of the hollow fiber, flows into the hollow fiber membrane, and is discharged to the outside of the hollow fiber membrane module. It passes through the pores from the inside of the hollow fiber, exits the outside of the hollow fiber, and is discharged to the outside of the hollow fiber membrane module. In addition, the backwash water after the backwashing process of the hollow fiber membrane module is discharged using the pipe which was the raw water inlet pipe of the hollow fiber membrane module during the filtration process of raw water without installing a separate pipe. In general, the backwashing of the hollow fiber membrane module is performed such that the backwash water is discharged through only one of the pipes connected to both ends of the hollow fiber membrane module (that is, the unidirectional backwashing). In addition, although it is possible to discharge through both pipes at both ends of the hollow fiber membrane module at the same time, even in this case, the rate of discharge through one pipe due to the characteristics of the pipe, the influence of gravity or uneven membrane contamination in the longitudinal direction of the hollow fiber, etc. The cursor is substantially similar to unidirectional backwashing.

However, since the hollow fiber membrane module is generally a long cylindrical shape, the backwash pressure during backwash may not be equally distributed in the longitudinal direction of the hollow fiber. In addition, even if the backwash pressure is equally distributed in the longitudinal direction of the hollow fiber, the portion of the hollow fiber membrane closer to the discharge pipe actually comes into contact with a greater amount of backwash water, thereby facilitating recovery of the filtration performance of the membrane. Therefore, in the case of the conventional backwashing in the unidirectional direction in the membrane module, there is a problem that non-uniform backwashing proceeds in the longitudinal direction of the hollow fiber membrane.

The development of a backwashing method capable of obtaining the maximum backwashing efficiency at the same backwashing quantity by preventing the non-uniform backwashing efficiency in the longitudinal direction of the hollow fiber membrane and recovering the membrane filtration performance uniformly as a whole.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method, a backwashing device and a water treatment device for sequentially backwashing a backwash water discharge direction of a hollow fiber membrane module in a bidirectional direction of a hollow fiber membrane in order to solve the above problems. will be.

In order to achieve the above object, the present invention includes first opening and closing means for discharging backwash water at both ends of the hollow fiber membrane module, and closes the second opening and closing means for a predetermined time and opens the first opening and closing means. Discharging the backwash water passing through the pores of the hollow fiber membrane to the outside of the membrane module through the first opening and closing means (1); And closing the first opening and closing means for a predetermined time and opening the second opening and closing means to discharge the backwash water passing through the hollow fiber membrane pores to the outside of the separation membrane module through the second opening and closing means. The backwash method of the hollow fiber membrane module, characterized in that.

The present invention also provides a method for backwashing a hollow fiber membrane module installed such that the backwash water inlet pipe of the membrane module faces the backwash water discharge pipe in the longitudinal direction of the hollow fiber membrane when the hollow fiber membrane module is an external pressure type.

In the backwashing method of the hollow fiber membrane module, the first opening and closing means is preferably mounted on the raw water inlet pipe of the hollow fiber membrane module during the filtration process of the raw water, the duration of step (2) is the step Less than the duration of (1) is preferable.

In addition, the present invention is a method for backwashing the hollow fiber membrane module, wherein the opening and closing means is an automatic valve, an automatic valve control device is connected to the automatic valve, the step (1) by the operation of the automatic valve control device And (2) provides a method for backwashing the hollow fiber membrane module, characterized in that to carry out.

In addition, the present invention is a hollow fiber membrane module; A backwash feed water storage tank for storing the backwash water of the hollow fiber membrane module; A backwash pressurized pump connected between the backwash feed water storage tank and the hollow fiber membrane module to supply backwash water from the backwash feed water storage tank to the hollow fiber membrane module; Backwash water discharge pipes connected to both ends of the hollow fiber membrane module; A first automatic valve (first open valve) and a second automatic valve (later open valve) mounted to the discharge pipe, respectively; And an automatic valve control device for alternately opening the first automatic valve and the second automatic valve in order.

The present invention also provides a backwashing apparatus for a hollow fiber membrane module in which the backwash water inlet pipe of the membrane module is opposed to the backwash water discharge pipe in the longitudinal direction of the hollow fiber membrane when the hollow fiber membrane module is an external pressure type.

Preferably, the backwash water discharge pipe equipped with the first automatic valve is a raw water inlet tube of the hollow fiber membrane module during filtration of raw water, and the automatic valve control device has an opening duration of the first automatic valve being the second automatic. Preferably, the automatic valve is opened by longer than the opening duration of the valve.

In the backwashing method and the backwashing apparatus of the hollow fiber membrane module, the pore size of the hollow fiber membrane is preferably 0.005 μm to 0.5 μm.

In another aspect, the present invention provides a hollow fiber membrane water treatment apparatus comprising a backwash device of the hollow fiber membrane module.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 1 shows an example of a bidirectional cross backwash process according to the present invention in a pressure-resistant hollow fiber membrane water treatment device. As shown in FIG. 1, the backwash feed water is supplied by the backwash pump 1 from the backwash water reservoir 8 to the separator module 10 through the automatic valve 5. First, when the automatic valve 3 at the bottom of the membrane module is closed and the automatic valve 2 at the top of the membrane module is opened, the backwash water is discharged through the automatic valve 4 through the discharge pipe in the direction ⓐ (step (1)). , Dotted lines). Subsequently, when the automatic valve 2 is closed and the automatic valve 3 is opened, the backwash water is discharged through the automatic valve 4 through the discharge pipe in the direction ⓑ (step (2), indicated by a dashed line).

The cross order of the reverse washing discharge direction, that is, the opening order in the discharge pipes in the ⓐ and ⓑ directions, is preferably to first open the discharge pipe which was the raw water inlet pipe of the membrane module during the filtration of raw water.

For example, when the raw water mainly containing particulate contaminants is supplied by the raw water inflow pump 7 in the hollow fiber membrane water purification treatment apparatus as shown in FIG. 2, only the automatic valve 2 is opened in the ⓒ direction, that is, the separation membrane. If raw water flows from the top of the module, the membrane fouling at the top of the separator module becomes more pronounced than the bottom. Therefore, when performing backwashing, the first automatic valve 2 is first opened and the backwash is preferentially performed in the direction ⓐ in FIG. 1, and then the automatic valve 2 is closed and the automatic valve 3 is opened to the ⓑ direction. By backwashing, the backwashing efficiency can be increased by bringing the upper part of the membrane module, which has become more contaminated with membranes, into contact with more backwashing water.

On the contrary, when raw water is supplied by the raw water inflow pump 7 by opening only the automatic valve 3, that is, if raw water flows in the direction ⓓ of FIG. 2, the membrane contamination of the lower part of the membrane module becomes remarkable. In this case, the automatic valve 3 is first opened and the back washing is first performed in the direction ⓑ of FIG. 1, and then the automatic valve 3 is closed and the automatic valve 2 is opened to perform the back washing in the direction ⓐ. Washing efficiency can be increased.

However, in case of raw water mainly containing dissolved contaminants, membrane contamination may be reduced near the inflow pipe of the membrane module when the raw water is treated through the hollow fiber membrane, so the backwashing is first performed in the opposite direction of the raw water inflow pipe. Needs to be. That is, the implementation order for each direction of the hollow fiber membrane bidirectional cross backwash in the present invention can be changed according to the properties of the raw water.

In addition, the backwashing efficiency of the pressure-resistant hollow fiber membrane module of the present invention varies depending on the distribution ratio of the backwashing duration of each stage. For example, when raw water flows in the ⓓ direction of FIG. 2 and the incoming portion of the raw water, ie, the membrane contamination of the lower part of the membrane module, is marked, total backwashing is performed in the ⓑ direction and then in the direction as described above. If you run for 1 minute, the backwashing efficiency will be changed by adjusting the duration of the backwashing time in the ⓑ direction to 45 seconds, the duration in the ⓐ direction to 15 seconds, or 50 seconds and 10 seconds respectively. The duration of step (1) is longer than the duration of step (2) in that increasing the duration of step (1) increases the backwashing efficiency by first performing backwashing of the membrane portion where membrane fouling becomes significant. It is desirable to.

Figure 3 shows an example of the bidirectional cross-wash back washing process according to the present invention in the external pressure hollow fiber membrane water treatment device. Generally, the external pressure hollow fiber membrane module has two pairs of inlet / outlet tubes unlike the internal pressure type (see FIG. 3). As shown in FIG. 3, the backwashing feed water from the backwashing water reservoir 8 by the backwashing pump 1 in a state in which the automatic valve 3 'is closed and only the automatic valve 2' is opened is separated from the membrane module ( 10), it is efficient to discharge the backwash water through the discharge pipe by only opening the automatic valve 2 from the automatic valves 2 and 3 of the discharge pipe for uniform backwashing of the membrane as a whole (Fig. 3). Ⓐ direction, dotted line). Subsequently, when only the automatic valve 3 'is opened and the backwash water is introduced into the membrane module, it is efficient to open only the automatic valve 3 and discharge the backwash water through the discharge pipe (see ⓑ in FIG. 3, indicated by a dotted line). . That is, the backwash water inlet pipe of the membrane module is preferably installed to face the backwash water discharge pipe in the longitudinal direction of the hollow fiber membrane.

On the other hand, the cross order of the backwash discharge direction of the external pressure hollow fiber membrane module with respect to raw water mainly containing particulate contaminants, that is, the backwash order in the ⓐ direction and the ⓑ direction, is used to filter raw water through the hollow fiber membrane module. It is preferable to set to open the raw water inlet pipe of the membrane module of the first. This is because, as in the backwash of the pressure-resistant module, the hollow fiber portion in which the membrane fouling becomes prominent in the external pressure hollow fiber membrane module can be brought into contact with a larger amount of the backwash water to increase the backwashing efficiency. For example, if the raw water is supplied to the hollow fiber membrane module through the automatic valve 2 during the filtration of raw water, the automatic valves 2 and 2 'are opened at the time of back washing, and the automatic valve at the filtration process of the raw water. If raw water is supplied to the hollow fiber membrane module via (3), the automatic valves (3) and (3 ') are opened during backwashing.

However, in the case of raw water mainly containing dissolved contaminants, it is necessary to perform backwashing by first setting the inflow pipe opposite to the raw water inflow pipe first as in the backwash of the pressure-resistant module. That is, the implementation order for each direction of the hollow fiber membrane bidirectional cross backwash in the present invention can be changed according to the properties of the raw water.

In addition, even in the bidirectional cross backwashing of the external pressure hollow fiber membrane module of the present invention, the backwashing efficiency is changed according to the distribution ratio of the backwashing durations of the stages, and as in the case of the pressure resistant type, the membrane is increased by increasing the duration of step (1). It is preferable that the duration of step (1) be longer than the duration of step (2) in that backwashing of the membrane portion where contamination is conspicuous is performed first to increase the backwashing efficiency.

Bidirectional cross-washing method and apparatus of the present invention can be applied to the hollow fiber membrane module, it is generally preferred to use a microfiltration or ultrafiltration membrane having a pore size of 0.005㎛ ~ 0.5㎛.

The backwash pressurized pump usable in the bidirectional crosswashing apparatus of the present invention is not particularly limited as long as it provides a flow rate and pressure necessary for backwashing, and a centrifugal pump, a constant pressure pump, or a metering pump can be used. In addition, the automatic valve usable in the present invention is not particularly limited as long as it can be opened and closed automatically by a control signal from the outside. In addition, the automatic valve control apparatus of the present invention is not particularly limited as long as it is a device that controls the automatic valves to sequentially cross open as described above, and is preferably a PLC (Programmable Logic Controller).

The present invention provides a hollow fiber membrane water treatment device using the bi-directional cross backwashing device.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited thereto.

Example 1

Pressure-resistant hollow fiber membrane module (material: cellulose derivative, pore size: 0.01 μm, effective membrane area: 7.2 m2), raw water inflow pump, backwash pump (“CR2-20”, manufactured by Grundfos) 80 LMH by installing a water treatment pilot plant (see FIG. 1) including an automatic valve ("Butterfly" (25φ), manufactured by Gemu) and a PLC ("Master-K200", LG Electronics) as an automatic valve controller. While producing the treated water with a constant flux of (l / m 2 · hr), a single product under conditions of 0.5 hour backwash cycle, 1 minute backwash time, 1.4 bar backwash pressure, and 4 ppm (Cl equivalent) of chlorine concentration in backwash water The change in interlayer differential pressure with time of operation was measured using a pressure gauge (0-6 bar, manufactured by Omega Inc.) while performing the reverse direction (direction ⓐ in FIG. 1) and bidirectional cross-washing.

Fig. 4 shows the results of the operation of the hollow fiber membrane water treatment pilot plant and shows the change in the intermembrane pressure difference of the hollow fiber membrane water treatment device by the respective backwashing methods. In the a-b section, the bidirectional cross backwashing of the present invention was performed. In the b-c section, the backwash was performed in a single direction (direction ⓐ in FIG. 1), and in the c-d section, the bidirectional cross backwashing of the present invention was performed again. As membrane fouling progresses, the interlayer differential pressure required to produce treated water at the same flow rate increases. When raw water properties or other conditions are the same, this increase in intermembrane pressure means a decrease in backwash efficiency. In the a-b section of FIG. 4, the interlayer differential pressure was maintained at 0.4 bar or less, and in the b-c section, the pressure was increased to 0.5 bar to 0.6 bar, and was reduced to 0.4 bar or less in the c-d section and maintained stable. In other words, it can be seen that bidirectional cross-washing is superior in backwashing efficiency of the membrane than back-washing in one direction.

Example 2

After operating the hollow fiber membrane water purification apparatus in Example 1 for a long time, the membrane filtration performance was lowered, except that the flux was changed to 70 LMH (L / m 2 · hr) so as to increase the pressure of TMP. Under the same conditions, unidirectional (directions ⓐ and ⓑ in Fig. 1) and bidirectional cross backwashing were performed to compare changes in the rate of increase of the interlayer differential pressure with operation time (see Fig. 5). In Fig. 5, in the case of unidirectional backwashing, the increase in the intermembrane differential pressure is apparent, but in the case of the bidirectional crosswashing of the present invention, the intermembrane differential pressure was maintained substantially constant for a longer time even under the above conditions. In other words, if the bidirectional cross-washing of the present invention is performed, the membrane filtration performance can be kept constant even after a long-term filtration treatment, unlike the case of the unidirectional back-washing.

Example 3

Filtration was performed for the same time as in Example 1 to allow membrane fouling to proceed in the same manner, and then unidirectional (direction ⓐ and ⓑ in FIG. 1) and bidirectional cross-washing were performed for the same time. In each backwash method, the backwash water discharged through the automatic valve 4 of FIG. 1 was collected, and the turbidity was measured using a turbidimeter (“1720D”, manufactured by HACH), and the average value was obtained.

TABLE 1

Backwashing method Turbidity of discharged backwash water (NTU) Single direction (ⓐ direction) backwash 31.5 Single direction (ⓑ) backwash 32.9 Two-way cross backwash 43.2

In the case of bidirectional cross backwashing according to the present invention, the turbidity in the backwashing water was averaged 43.2 NTU, which was more than 30% higher than the other cases. The high turbidity of the discharged backwash water means more effective removal of membrane contaminants during backwashing, which indicates that the backwashing efficiency of bidirectional crosswashing is high.

Example 4

Pressure-resistant hollow fiber membrane module (material: cellulose derivative, pore size: 0.01㎛, effective membrane area: 64㎡), raw water inflow pump, backwash pump (“MVI 5.5HP”, manufactured by Wilo) in Hwaseong, Korea And a purified water treatment pilot plant (see FIG. 1) including a PLC ("Glofa-GM", manufactured by LG Industrial Co., Ltd.) as an automatic valve control device, and treated water at a constant flow rate of 60 LMH (L / m 2 · hr). During production, bidirectional cross-washing was performed under conditions of 1.25 h backwashing cycle, 1 min backwashing time, 0.7 bar backwashing pressure and 4 ppm chlorine concentration in backwashing water in terms of Cl. As the duration was changed, a change in the interlayer differential pressure according to the operating time was measured using a pressure gauge (0 to 6 bar manufactured by Keller), and the results are shown in FIG. 6.

In the section a-b of FIG. 6, first backwashing was performed for 30 seconds so that the backwashing water was discharged through the inlet pipe of the raw water during the filtration treatment, and then reverse washing was performed for 30 seconds. In the b-c section, backwashing was conducted for 45 seconds so that backwashing water was discharged through the inlet pipe of raw water, and then reverse washing was performed for 15 seconds. In FIG. 6, the interlayer differential pressure was significantly decreased and stable in the b-c section rather than the a-b section. Therefore, in the case of bidirectional cross backwashing of the hollow fiber membrane module of the present invention, it is understood that it is preferable to continue the first step of discharging the backwash water through the raw water inlet pipe of the membrane module during the filtration process of the raw water longer than the second step. Can be.

According to the present invention, in the backwashing method of sequentially performing the reverse washing water discharge direction of the hollow fiber membrane module in both directions in the longitudinal direction of the hollow fiber membrane, the reverse washing direction priority order and angle according to the inflow direction and the water quality of the raw water Differential allocation of the backwashing time in the direction to induce uniform backwashing of the hollow fiber membrane can perform backwashing with superior efficiency compared to the conventional one-way backwashing.

1 is a process chart showing the flow of backwash water in a backwash apparatus and a water treatment apparatus including the same of a pressure-resistant hollow fiber membrane module using a bidirectional crosswashback method according to the present invention.

FIG. 2 is a flowchart illustrating the flow of raw water during filtration of raw water using the purified water treatment device of FIG. 1.

Figure 3 is a process chart showing the flow of backwash water in the backwashing device of the external pressure hollow fiber membrane module using the bidirectional cross-washback method according to the present invention and the water treatment device including the same.

FIG. 4 is a graph illustrating a change in transmembrane pressure (TMP) of the hollow fiber membrane water purification apparatus by the respective backwashing methods as a result of backwashing experiments of the hollow fiber membrane module according to Example 1. FIG.

FIG. 5 is a graph illustrating a change in the intermembrane pressure difference of the hollow fiber membrane water purification apparatus by the respective backwashing methods after a long period of operation as a result of the backwash experiment of the hollow fiber membrane module according to Example 2. FIG.

FIG. 6 is a graph illustrating a change in the interlayer differential pressure according to a change in the duration of the backwashing step in each direction of the bidirectional cross-washing method of the present invention as a backwashing test result of the hollow fiber membrane module according to Example 4. FIG. .

<Description of Drawing>

1: backwash pump 5: automatic valve (for backwash water supply)

2: Automatic valve (in backwash water discharge pipe) 6: Automatic valve (for treated water collection)

3: Automatic valve (in backwash water discharge pipe) 7: Raw water inflow pump

2´: Automatic valve (in backwash water inlet) 8: Backwash water storage tank

3´: automatic valve (in backwash water inlet) 9: raw water reservoir

4: automatic valve (for backwash water discharge) 10: hollow fiber membrane module

Claims (12)

In the reverse washing method of the hollow fiber membrane module, the first opening and closing means for discharging the backwash water is provided at both ends of the hollow fiber membrane module, the second opening and closing means for a predetermined time and the first opening and closing Discharging the backwash water passing through the pores of the hollow fiber membrane to the outside of the membrane module through the first opening and closing means (1) by opening the means; And (2) closing the first opening / closing means for a predetermined time and opening the second opening / closing means to discharge the backwash water passing through the hollow fiber membrane pores to the outside of the membrane module through the second opening / closing means. , The first opening and closing means is mounted on the raw water inlet pipe of the hollow fiber membrane module during the filtration process of raw water, the duration of the step (1) is hollow fiber, characterized in that longer than the duration of the step (2) Backwashing method of membrane module. The method of claim 1, The hollow fiber membrane module is an external pressure type, and the backwash water inlet pipe of the membrane module is installed to face the backwash water discharge pipe in the longitudinal direction of the hollow fiber membrane. delete delete The method according to claim 1 or 2, The opening and closing means is an automatic valve, the automatic valve control device is connected to the automatic valve, the operation of the automatic valve control device of the hollow fiber membrane module characterized in that performing the steps (1) and (2) Backwash method. The method according to claim 1 or 2, The pore size of the hollow fiber membrane is 0.005㎛ ~ 0.5㎛ backwash method of the hollow fiber membrane module, characterized in that. Hollow fiber membrane module; A backwash feed water storage tank for storing the backwash water of the hollow fiber membrane module; A backwash pressurized pump connected between the backwash feed water storage tank and the hollow fiber membrane module to supply backwash water from the backwash feed water storage tank to the hollow fiber membrane module; Backwash water discharge pipes connected to both ends of the hollow fiber membrane module; First and second automatic valves respectively mounted to the discharge pipe; And an automatic valve control device for sequentially opening the first automatic valve and the second automatic valve alternately, wherein the backwash water discharge pipe equipped with the first automatic valve has a raw water inflow from the hollow fiber membrane module during filtration of raw water. And the automatic valve control device opens the automatic valve by opening the first automatic valve longer than the opening duration of the second automatic valve. The method of claim 7, wherein The membrane module is an external pressure type, and the backwash water inlet pipe of the membrane module is backwashing device of the hollow fiber membrane module, characterized in that installed in the longitudinal direction of the backwash water discharge pipe and the hollow fiber membrane. delete delete The method according to claim 7 or 8, The pore size of the hollow fiber membrane is 0.005㎛ ~ 0.5㎛ backwash apparatus of the hollow fiber membrane module. A hollow fiber membrane water treatment device, comprising the backwashing device of claim 7.