JP2001054789A - Backwashing method of internal pressure type hollow fiber membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backwashing method efficiently backwashing an internal pressure type hollow fiber membrane. SOLUTION: In this method, a cross flow filter type membrane treating device using the internal pressure type hollow fabric membrane is backwashed by intermittently feeding backwashing water to the membrane outside with raw water allowed to flow into the internal side of the hollow fabric membrane of a membrane module 5. Namely while raw water is allowed to flow toward a circulation water outflow port 7 from a raw water feed part 4 by continuously operating a circulation pump 3, the backwashing water under a specified pressure is intermittently fed from a treating water outflow part 6, and a backwashing state in which membrane external pressure becomes high by feeding the backwashing water, and a swelling state in which membrane internal pressure becomes high by feeding only raw water, are repeated with a proper interval, for example, every several seconds. Besides, while the flow direction of raw water fed into the inside of the hollow fabric membrane is switched, the backwashing is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for back washing internal pressure type hollow fiber membranes, and more particularly, to a method for internal pressure type membrane treatment using hollow fiber membranes having high permeability and hollow fiber membranes having a large inner diameter. It relates to a back washing method.

[0002]

2. Description of the Related Art A membrane treatment apparatus using an internal pressure type hollow fiber membrane usually supplies backwash water to a permeated water side (outside) of the hollow fiber membrane at regular intervals. Backwashing is performed to remove dirt attached to the raw water side (inside) of the membrane. However, in the conventional method, the pressure on the outside of the hollow fiber membrane is increased during the back washing, so that a high porosity, a hollow fiber membrane having a high permeability such as a thin wall, and a hollow fiber membrane having a large inner diameter are not suitable for the conventional method. In addition, since the film shrinks due to the external pressure, dirt attached to the inside cannot be sufficiently removed.

Accordingly, an object of the present invention is to provide a backwashing method capable of efficiently performing backwashing of an internal pressure type hollow fiber membrane.

[0004]

Means for Solving the Problems To achieve the above object, a method for back washing an internal pressure type hollow fiber membrane according to the present invention is directed to an internal pressure type hollow fiber membrane for supplying raw water to the inside of the hollow fiber membrane and performing a filtration operation. Backwashing method, characterized in that the backwash water is intermittently supplied to the outside of the hollow fiber membrane while the raw water is circulated inside the hollow fiber membrane, and the flow direction of the raw water is alternately changed. It is characterized in that it is performed while switching.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram showing an example of a cross-flow filtration type membrane processing apparatus using an internal pressure type hollow fiber membrane, and FIG. 2 is a partial cross-sectional perspective view showing an example of an internal pressure type hollow fiber membrane module. FIG. 3 and FIG. 3 are explanatory views showing a state at the time of back washing, and FIG.
Is an enlarged view of a hollow fiber membrane part.

First, a cross-flow filtration type membrane treatment apparatus using an internal pressure type hollow fiber membrane shown in FIG. To the inside of the hollow fiber membrane of the membrane module 5, the water (membrane filtered water) permeating through the hollow fiber membrane flows out from the treated water outlet 6, and a part of the raw water is circulated through the circulating water outlet 7 3 to be circulated upstream.

As shown in FIG. 2, the membrane module 5 contains a large number of hollow fiber membranes 11 sealed at both ends in a cylindrical case 10 in a state of being wrapped by a protective net 12. A raw water supply section 4 is provided at one end of the case 10, a circulating water outflow section 7 is provided at the other end, and a treated water outflow section 6 is provided at the body.

In the present invention, the back washing in such a membrane treatment apparatus is performed intermittently on the outside of the membrane while the raw water is circulated inside the hollow fiber membrane of the membrane module 5 as shown in FIG. Supply backwash water to That is, while the circulation pump 3 is continuously operated to flow raw water from the raw water supply unit 4 to the circulating water outflow unit 7,
As shown in FIG. 4 (A), backwash water at a predetermined pressure is intermittently supplied from above, and as shown in FIG. The backflush of the hollow fiber membrane 11 is performed by repeating the expansion state in which the pressure inside the membrane is increased by supplying only the raw water at appropriate intervals, for example, every few seconds.

By performing the back washing of the hollow fiber membrane 11 in this manner, the back washing water can act on the hollow fiber membrane 11 that has been swollen by the supply of raw water, so that the conventional hollow fiber membrane shrinks. The backwash water can be made to act more effectively as compared with the conventional method in a state of being left. In addition, by supplying the backwash water intermittently, the state in which the hollow fiber membrane 11 is expanded by the pressure of the raw water and the state in which the hollow fiber membrane 11 contracts by the pressure of the backwash water are repeated. Dirt adhering to the inner surface is easily detached, and the cleaning effect can be increased.

Further, by performing the above-described back washing while switching the flow direction of the raw water supplied to the inside of the hollow fiber membrane 11, dirt on the inner surface of the membrane can be effectively removed, so that the effect of the back washing is further improved. Can be improved.

[0011]

As described above, according to the internal pressure type hollow fiber membrane backwashing method of the present invention, the backwash water is intermittently supplied to the expanded hollow fiber membrane by supplying raw water. Since the backwashing is performed, the backwashing of a hollow fiber membrane having high permeation performance or a hollow fiber membrane having a large inner diameter can be efficiently performed.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a cross-flow filtration type membrane treatment apparatus using an internal pressure type hollow fiber membrane.

FIG. 2 is a partially sectional perspective view showing an example of an internal pressure type hollow fiber membrane module.

FIG. 3 is an explanatory diagram showing a state at the time of back washing.

FIG. 4 is an enlarged view of a hollow fiber membrane part.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Raw water tank, 2 ... Raw water pump, 3 ... Circulation pump, 4 ... Raw water supply part, 5 ... Membrane module, 6 ... Treated water outflow part, 7 ...
Circulating water outlet, 10 ... case, 11 ... hollow fiber membrane, 12 ...
Protection net

Claims (2)

[Claims] 1. A method for back washing an internal pressure type hollow fiber membrane in which raw water is supplied to the inside of the hollow fiber membrane to perform a filtration operation, wherein the raw water is circulated inside the hollow fiber membrane while the raw water is circulated inside the hollow fiber membrane. Backwashing method for an internal pressure type hollow fiber membrane, characterized in that backwash water is intermittently supplied to the hollow fiber membrane. 2. The method of back washing an internal pressure type hollow fiber membrane according to claim 1, wherein the method is performed while alternately switching the flow direction of the raw water.