JPH057744A - Membrane washing apparatus - Google Patents

Abstract

PURPOSE:To efficiently release and wash the contaminant bonded to the surfaces of the membranes of a membrane module. CONSTITUTION:A membrane washing apparatus is equipped with a membrane module 4, a washing water tank 10 storing washing water containing a fibrous substance and systems 12,11 supplying washing water to the membrane module 4. Therefore, the surface of a membrane is easily and efficiently washed within a short time by the good physical washing effect due to the fibrous substance without generating trouble such as the damage of the surface of the membrance and membrane capacity can be restored in a high restoration rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane cleaning device, and more particularly to an MF (microfiltration) membrane, a UF (ultrafiltration) membrane, and an RO.
(Reverse osmosis) The present invention relates to a membrane cleaning device capable of efficiently peeling and cleaning contaminants attached to the membrane surface of a membrane module such as a membrane.

[0002]

2. Description of the Related Art In a membrane separation process using a membrane separation device, contaminants adhere to the membrane surface of a membrane module over time due to the operation of the device, increasing the pressure loss of the membrane, causing clogging and permeation of the membrane. Problems such as reduced flux occur.

[0003] In order to reduce the problem caused by such sludge adherence, various measures have hitherto been made in the structure of the membrane module for preventing the sludge adherence. For example,
In order to prevent the formation of a gel layer on the membrane surface in cross-flow filtration, the applicant of the present invention has proposed a filter plate structure in which the membrane surface of a flat plate type membrane module is made uneven. Further, recently, a spiral wound type membrane module using a corrugated sheet spacer has been put into practical use.

On the other hand, as a method for removing contaminants adhering to the membrane surface, a method of washing the membrane surface with washing water mixed with fine particles such as activated carbon or ion exchange resin (physical washing method), or an appropriate method A method of cleaning the film surface with a chemical solution (chemical cleaning method) is used.

[0005]

The above-mentioned conventional membrane module structure for preventing contaminants from adhering and the membrane surface cleaning method for removing contaminants have both advantages and disadvantages.
Although there is a tentative effect, a sufficiently satisfactory effect has not been obtained. In particular, regarding the membrane surface cleaning method, although various methods are adopted depending on the properties of the liquid to be treated of the membrane separation device, etc., since a sufficient cleaning effect is not obtained,
Under the present circumstances, further improvement is desired.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide a membrane cleaning apparatus capable of efficiently peeling and cleaning contaminants attached to the membrane surface of a membrane module.

[0007]

Means for Solving the Problems The membrane cleaning apparatus of the present invention comprises:
It is characterized by comprising a wash water tank for storing wash water containing a fibrous substance, and a system for supplying the wash water in the wash water tank to the membrane module.

The present invention will be described in detail below. In the membrane cleaning apparatus of the present invention, as the fibrous substance to be contained in the cleaning water, a substance such as cellulose, synthetic polymer or the like that is resistant to acids and alkalis and does not damage the membrane surface of the membrane module Is preferable, and specifically,
Examples of the synthetic polymer fine particles such as cellulose powder and polystyrene powder particles obtained from pulp raw material have a fiber length of 50 to 200 μm and a fiber width of 10 to 50 μm.

As the washing water used in the present invention, washing water obtained by suspending the above fibrous substance in water can be suitably used, but preferably, the following fibrous materials are used. The synergistic effect of the physical cleaning with the substance and the chemical cleaning with the chemical solution provides a remarkably high cleaning effect, which is extremely advantageous.

Washing water in which a fibrous substance is suspended in a chemical solution such as acid or alkali is used. Washing water in which a fibrous substance is suspended in water and a chemical solution are used. After washing with washing water in which a fibrous substance is suspended in water, the washing is performed with a chemical solution. The fibrous substance is circulated and washed with washing water suspended in water, and after a predetermined time, a chemical (or a chemical solution) is added to the washing water.

The content of the fibrous substance in the wash water is
Although it depends on the type of cleaning water, the properties of the contaminants attached to the membrane surface, and the amount of contaminants, usually 10 to 50 g / l when suspending fibrous substances in water, chemicals such as acids or alkalis When suspended in a solution, the amount is preferably 5 to 20 g / l. If the amount of this fibrous substance is too small, the sufficient effect of removing contaminants according to the present invention cannot be obtained, and conversely, if it is too large, the circulation efficiency of washing water decreases, so the above range is preferred.

In the present invention, the membrane module is not particularly limited, but preferably has a membrane module structure having a high effect of preventing attachment of the above-mentioned contaminants, that is, a spiral type membrane module or flat membrane having corrugated plate spacers inserted therein. Preferred are mold membrane modules, especially spiral membrane modules. By applying the present invention to a membrane module having such a structure that contaminants are unlikely to adhere to the membrane surface, an even better cleaning effect can be achieved.

That is, for example, when the spiral type membrane module in which the corrugated sheet spacer is inserted is washed with washing water in which a fibrous substance is suspended in an acid-based chemical aqueous solution, the fibrous substance is generated due to the turbulent flow effect of the corrugated sheet spacer. The effect of removing contaminants by the substance is further enhanced, and the synergistic effect of both effects allows the contaminants adhering to the film surface to be efficiently removed. In particular, when the pollutant is an inorganic substance such as iron oxide or calcium carbonate, the acid-based chemical in the wash water accelerates the dissolution reaction of the pollutant and further enhances the washing effect.

When the contaminants adhering to the film surface are mainly composed of organic substances, it is preferable to use washing water in which fibrous substances are suspended in an alkaline chemical solution.

The washing water after the contaminants adhering to the membrane surface are stripped and washed, that is, the washing waste liquid is subjected to waste liquid treatment (for example, treatment such as neutralization, coagulation, precipitation, filtration separation) as required. However, in this case, the waste liquid can be efficiently treated by the contained fibrous substance. That is, for example, a waste liquid containing iron oxide, aluminum oxide, or the like, which is a biological contaminant, is washed with acid-based chemical cleaning water containing fibrous substances, and is subjected to solid-liquid separation after neutralization with an alkaline agent. In this case, the fibrous substance effectively acts as a filter aid or a coagulant, and the solid-liquid separation treatment can be efficiently performed.

[0016]

By the good peeling effect of the fibrous substance, the contaminants attached to the film surface can be easily and efficiently peeled and removed without damaging the film surface. In particular, the combined use of chemicals in the cleaning water enhances the cleaning effect even further, and with a small amount of fibrous material used, efficient stripping cleaning can be performed in a short time, and the permeation flux of the membrane is almost completely restored. It is possible to

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing an embodiment of the membrane cleaning apparatus of the present invention.

In FIG. 1, 1 is a pipe for introducing raw water into the raw water tank 2, 3 is a pipe for feeding the raw water in the raw water tank 2 to the membrane module 4, a valve V ₁ , a circulating water pump 5, and a pressure. It has a total of 6. Reference numeral 7 is a pipe for discharging the membrane permeated water of the membrane module 4 as treated water, and 8 is a pipe for returning the concentrated water of the membrane module 4 to the raw water tank 2. The pipe 8 is provided with a valve V ₂ and a flow meter 9. A washing water tank 10 is connected to a washing water return pipe 11 branched from a pipe 8 and a washing water supply pipe 12 connected to the pipe 3.
The wash water return pipe 11 and the wash water supply pipe 12 are provided with valves V ₃ and V ₄ , respectively.

When performing membrane separation treatment such as filtration of raw water and desalting, first, valves V ₁ and V ₂ are opened, and valves V ₃ and V ₂ are opened.
While closing ₄ and starting the circulating water pump 5, the raw water in the raw water tank 2 is supplied to the membrane module 4 via the pipe 3, and the permeated water is taken out as the treated water from the pipe 7,
The concentrated water is circulated in the raw water tank 2 through the pipe 8.

Continuing such membrane separation treatment causes contaminants to adhere to the membrane surface of the membrane module 4,
The decrease of the permeation velocity and the increase of the loss of force cause the pressure gauge 6 and the flowmeter 9
After the confirmation, the circulating water pump 5 is once stopped, the valves V ₁ and V ₂ are closed, and the valves V ₃ and V ₄ are opened.
The circulation water pump 5 is started again, the cleaning water in the cleaning water tank 10 is supplied to the membrane module 4 via the cleaning water supply pipe 12 and the pipe 3, and then returned to the cleaning water tank 10 through the cleaning water return pipe 11. The washing cleans the membrane surface of the membrane module 4.

During this cleaning, the fibrous substance contained in the cleaning water allows the contaminants adhering to the film surface to be efficiently peeled and removed.

Further, the cleaning waste liquid is withdrawn from the cleaning water tank 10 or the cleaning water return pipe 11 as required and used for waste liquid treatment. In that case as well, as described above, due to the action of the fibrous substance. , Efficient processing can be performed.

In the apparatus shown in the figure, the opening and closing of the valve, the starting and stopping of the pump are controlled by a computer in conjunction with the measured values of the pressure gauge and the flow meter, so that the membrane separation process and the membrane cleaning are automatically performed. be able to.

The present invention will be described in more detail below with reference to experimental examples. Experimental Example 1 Raw water (city water) was passed through the device shown in FIG. 1 (the setting conditions of the membrane module are as follows) to perform desalination treatment. Membrane module setting conditions Membrane module configuration: Polyamide RO membrane with corrugated sheet spacer inserted (membrane area = 25 cm ² ) Membrane surface flux: 0.5 m / s sec Membrane surface pressure: 7 kg / cm ² Permeation flux: 0 .85m ³ / m ² · day When the treatment was continuously carried out, after 10 days, a permeation flux of 0.50m ³ / m ² · day and the membrane performance such as desalination rate deteriorated. Therefore, the membrane was washed with the washing water shown in Table 1 for the time shown in Table 1. The following were used as fibrous substances. Fibrous substance KC Floc W100 (manufactured by Sanyo Kokusaku Pulp Co., Ltd.) (Cellulose powder obtained from pulp raw material) Particle size: 100 mesh pass 90% or more Average fiber length: about 80 μm Average particle size (fiber width): About 10 μm After washing Table 1 shows the permeation flux of and the recovery rate of the permeation flux obtained by the following formula.

[0025]

[Equation 1]

[0026]

[Table 1]

As is clear from Table 1, according to the present invention, the contaminants on the membrane surface can be efficiently stripped and washed, and the permeation flux of the membrane can be recovered with a high recovery rate of 90% or more. . Especially when combined with chemical cleaning (No. 3),
With a small amount of fibrous material, the permeation flux can be almost completely recovered in a short cleaning time of about 1/4 of the conventional (No. 1) cleaning time. Then, with the recovery of the permeation flux, the desalination rate of the RO membrane was also fully recovered.

[0028]

As described in detail above, according to the membrane cleaning apparatus of the present invention, the contaminants adhering to the membrane surface of the membrane module are removed by the good physical cleaning effect of the fibrous substance contained in the cleaning water. It is possible to easily and efficiently perform stripping cleaning in a short time without causing defects such as membrane surface damage, and to recover membrane performance such as pressure loss, permeation flux, and desalination rate at a significantly high recovery rate. . According to the present invention, it is possible to maintain a high membrane performance of the membrane module and perform stable and efficient membrane separation treatment.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a membrane cleaning apparatus of the present invention.

[Explanation of symbols]

 2 Raw water tank 4 Membrane module 10 Washing water tank

Claims (1)

Claim: What is claimed is: 1. An apparatus for cleaning a membrane module, comprising a cleaning water tank for storing cleaning water containing a fibrous substance, and the cleaning water in the cleaning water tank to the membrane module. A film cleaning apparatus comprising: a supply system.