JP3866393B2 - Cleaning method for hollow fiber membrane module - Google Patents

Description

【図面の簡単な説明】
【図１】本発明の洗浄方法を説明するためのフロー図である。
【図２】本発明の洗浄方法に適した中空糸膜モジュールを示す模式図である。
【符号の説明】
１、２ ポンプ
３〜７ バルブ
８ 中空糸膜モジュール
９ エアーベント
１０ 薬液タンク[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cleaning a hollow fiber membrane module, and more particularly to a method for cleaning a hollow fiber membrane module when filtering a highly pollutant (particularly organic matter) liquid.
[0002]
[Prior art]
Conventionally, hollow fiber membrane modules have been widely used in the field of so-called microfiltration such as the production of aseptic water, drinking water and high-purity water, and purification of air. Recently, secondary treatment and tertiary treatment in sewage treatment plants Highly polluted water such as solid-liquid separation in septic tanks, solid-liquid separation of ss (suspended suspended solids) in industrial wastewater, direct filtration of river water in water purification plants, filtration of industrial tap water, filtration of pool water, etc. Studies for use in processing are being conducted in various forms.
[0003]
However, in these applications, the filtration membrane clogged as filtration continued, and the filtration differential pressure increased. The clogging of the filtration membrane is roughly classified into two, and one is accumulation of fine particles or the like on the membrane surface. On the other hand, it can wash | clean by cross-flow filtration or the scrubbing washing | cleaning by a gas-liquid mixed flow. The other is fouling derived from the adsorption of organic substances, minute inorganic elements, and the like. Cleaning with chemicals is indispensable for cleaning fouling.
[0004]
[Problems to be solved by the invention]
The chemical cleaning is generally performed by separately preparing a chemical bath for immersing the hollow fiber membrane module and immersing the module in the chemical bath for cleaning, and the cleaning effect is high. However, this method requires a module attachment / detachment operation, and the operation is complicated.
[0005]
As an alternative method, a method of cleaning the module in-line has been studied. As a general cleaning method, a method in which a cleaning chemical solution is reversely passed from the hollow portion to the outside during cleaning is employed for a hollow fiber membrane module that performs filtration from the outside of the hollow fiber membrane toward the hollow portion. However, when this method is applied to a hollow fiber membrane module having a large membrane area, the chemical solution oozes out from the hollow fiber membrane surface before the chemical solution spreads over the entire hollow fiber membrane in the module, The chemical cleaning was difficult.
[0006]
The objective of this invention is providing the washing | cleaning method of the hollow fiber membrane module which can carry out chemical | medical solution washing | cleaning simply in-line.
[0007]
[Means for Solving the Problems]
That is, in the present invention, when cleaning a hollow fiber membrane module for liquid filtration that performs filtration from the outside of the hollow fiber membrane toward the hollow portion, a cleaning chemical solution was passed through the hollow portion of the hollow fiber membrane and circulated. The method for cleaning a hollow fiber membrane module is characterized in that the step of pressurizing the hollow portion of the hollow fiber membrane and passing the cleaning chemical solution through the hollow fiber membrane is performed at least once.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a method for cleaning a hollow fiber membrane module of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an example of the cleaning method of the present invention.
[0009]
As the hollow fiber membrane module filtration system to which the cleaning method of the present invention is applied, it is possible to adopt any of suction suction filtration, self-weight filtration due to water head difference and pressure filtration in which a module is mounted in a pressure can body. An explanation will be given taking pressure filtration as an example.
[0010]
During normal pressure filtration using a hollow fiber membrane module, the pump 1 is operated to open the valve 3, and the valves 4, 5, 6, and 7 are closed to perform filtration. On the other hand, at the time of cleaning, the pump 2 is operated, the valves 3, 4, 7 are closed, the valves 5, 6 are opened, and the chemical solution is passed from the chemical solution tank 10 into the hollow portion of the hollow fiber membrane for circulation. After sufficient circulation and the inside of the hollow portion of the hollow fiber membrane is replaced with the chemical solution, the pump 2 is stopped, the valves 4 and 7 are opened, the valves 3, 5, and 6 are closed, and the hollow fiber membrane hollow is applied by applying air pressure. The chemical solution in the section is passed through the membrane wall in the reverse direction to the outside of the hollow fiber membrane. By this operation, the fouling in the membrane wall (inside the membrane) of the hollow fiber membrane of the hollow fiber membrane module 8 is chemically cleaned.
[0011]
The structure of the hollow fiber membrane module can be broadly divided into a both-end resin fixing type in which both ends of the hollow fiber membrane are separately fixed with a resin, and the hollow fiber membrane is converged into a U shape and fixed with a resin or hollow fiber There is a single-end resin fixing type in which one end of the membrane is sealed and the open end of one end is fixed with resin. However, a double-end resin fixing type is preferable as the hollow fiber membrane module used in the method of the present invention. This is because in the case of the both-end resin-fixed type, it is possible to easily and reliably carry out the circulation of the cleaning chemical liquid into the hollow portion of the hollow fiber membrane.
[0012]
The chemical used as the cleaning chemical in the cleaning method of the present invention is not particularly limited as long as it can dissolve or oxidatively decompose the fouling substance without damaging the hollow fiber membrane and the members constituting the filtration system. Specific examples thereof include sodium hypochlorite, chloramine, hydrogen peroxide, caustic soda, hydrochloric acid, oxalic acid, and citric acid.
[0013]
The material of the hollow fiber membrane to which the cleaning method of the present invention is applied is not particularly limited, and any material such as polyolefin, polysulfone, PAN, and cellulose can be used. In view of the high chemical resistance and the high strength of the film, a polyolefin-based material is preferable.
In the cleaning method of the present invention, the cleaning chemical solution is passed through the hollow portion of the hollow fiber membrane and circulated so that the inside of the hollow portion of the hollow fiber membrane is completely replaced with the chemical solution and the chemical solution is added to the inside of the hollow fiber membrane. It is for making it fully contact. When the liquid circulation time is short, the contact of the chemical with the membrane is insufficient, and sufficient cleaning cannot be achieved. The liquid circulation time is preferably about 20 seconds to 3 hours. The pressurizing operation after circulating the chemical solution may be carried out continuously, or by intermittently pressurizing several times, the cleaning chemical solution penetrates into the membrane to dissolve the fouling substance, etc. Later, this can be replaced with a new cleaning chemical. Although the time for the pressurizing operation varies depending on the cleaning power of the chemical solution, it is usually preferably about 5 seconds to 20 minutes per time.
[0014]
FIG. 2 shows a hollow fiber membrane module suitable for carrying out scrubbing cleaning, and a hollow fiber membrane made of a knitted fabric having a hollow fiber membrane as a weft is perpendicular to the hollow fiber membrane while keeping its end open. A hollow fiber membrane module is shown in which both ends of a hollow fiber membrane are separately fixed with a synthetic resin so that the cross-sectional shape is a long and substantially rectangular shape. The cleaning method of the present invention can be effectively applied to this type of hollow fiber membrane module.
[0015]
【Example】
EXAMPLE By carrying out the activated sludge solid-liquid separation of domestic wastewater by the immersion suction filtration method using the hollow fiber membrane module (STELLAPORE L, trade name, manufactured by Mitsubishi Rayon Co., Ltd.) having the shape shown in FIG. Three cleaning test modules (modules A, B, and C) in which clogging occurred were prepared. The differential pressure of the hollow fiber membrane module at the beginning of filtration was 5 kPa, and the differential pressure after clogging was 35 kPa.
[0016]
Module A was cleaned by immersing it in a chemical tank of 2000 ppm sodium hypochlorite aqueous solution for 2 hours. As for module B, a pressure of 100 kPa was applied to 5 L of 2000 ppm sodium hypochlorite aqueous solution to allow the solution to pass from the hollow portion side to the outside of the hollow fiber membrane for about 5 minutes.
Module C was cleaned according to the method of the present invention. That is, the hollow fiber membrane module is attached to a chemical pipe as shown in FIG. 1, and a 2000 ppm sodium hypochlorite aqueous solution is supplied by a pump so as to flow in the hollow portion of the hollow fiber membrane, The liquid was circulated. Thereafter, an air pressure of 100 kPa was applied for 5 minutes to push out all the chemical solution inside the hollow fiber membrane module to the primary side.
The differential pressure of each hollow fiber membrane module after the chemical solution washing was as shown in Table 1. The hollow fiber membrane module C to which the cleaning method of the present invention was applied achieved a cleaning effect equivalent to that of the hollow fiber membrane module A to which the cleaning method immersed in a chemical solution was applied.
[0017]
[Table 1]

[Brief description of the drawings]
FIG. 1 is a flowchart for explaining a cleaning method of the present invention.
FIG. 2 is a schematic view showing a hollow fiber membrane module suitable for the cleaning method of the present invention.
[Explanation of symbols]
1, 2 Pump 3-7 Valve 8 Hollow fiber membrane module 9 Air vent 10 Chemical tank

Claims (3)

When washing a hollow fiber membrane module for liquid filtration that performs filtration from the outside of the hollow fiber membrane toward the hollow part, after passing a cleaning chemical solution through the hollow part of the hollow fiber membrane and circulating it, A method for cleaning a hollow fiber membrane module, wherein the step of pressurizing the hollow portion and passing the cleaning chemical solution through the hollow fiber membrane surface is performed at least once. The method for cleaning a hollow fiber membrane module according to claim 1, wherein the hollow fiber membrane module is of a type in which both ends of the hollow fiber membrane are separately fixed with resin. The method for cleaning a hollow fiber membrane module according to claim 1 or 2, wherein the hollow fiber membrane is made of polyolefin.

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