JP2003024754A - Membrane module washing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane module washing method capable of performing the regeneration treatment of activated carbon simultaneously with the washing treatment of a membrane module, capable of extending the life of the membrane module and capable of reducing equipment cost or operation cost in the whole of treatment equipment. SOLUTION: In the method for washing the membrane module performing the solid-liquid separation of raw water in which powdery activated carbon is charged, hydrogen peroxide is added to the raw water so as to set the concentration of hydrogen peroxide in raw water to 10%. This hydrogen peroxide- containing raw water is brought into contact with the membrane module not only to wash the membrane module but also to perform the regeneration treatment of activated carbon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a membrane module, and more particularly, a method for cleaning a membrane module in which powdered activated carbon effective for removing soluble organic substances in raw water is added and mixed in raw water for membrane filtration. Regarding the method.

[0002]

2. Description of the Related Art As means for separating solids in raw water,
In recent years, solid-liquid separation has been performed using a separation membrane. A solid-liquid separator using this separation membrane can be treated by immersing a membrane module consisting of a flat membrane or a hollow fiber membrane in the treatment tank. It has the advantage that

Further, since the soluble organic substances and odorous components contained in the raw water cannot be removed only by the separation membrane, activated carbon is introduced into the raw water and adsorbed on the activated carbon to remove it from the raw water. Activated carbon is separated by a separation membrane and reused.

[0004]

However, in solid-liquid separation by membrane separation, solids adhere to and deposit on the filtration surface of the membrane module, so it is necessary to regularly wash the membrane module with chemicals. Against this, it was necessary to perform a periodical regeneration treatment different from the membrane module. However, it was substantially impossible to completely separate and recover the activated carbon from the membrane module for this regeneration treatment.

Further, the normal chemical cleaning of the membrane module is
Since the membrane module is transferred to a cleaning tank provided separately from the treatment tank, this is a cause of complication of the water treatment system. Furthermore, it was necessary to treat the cleaning waste liquid and rinse waste liquid generated during chemical cleaning.

Therefore, according to the present invention, the cleaning treatment of the membrane module and the regeneration treatment of the activated carbon can be performed at the same time, so that not only the life of the membrane module can be extended but also the facility cost and the operating cost of the entire treatment facility can be reduced. It is intended to provide a method for cleaning a module.

[0007]

In order to achieve the above object, a method for cleaning a membrane module of the present invention is a method for cleaning a membrane module in which raw water charged with powdered activated carbon is subjected to solid-liquid separation. It is characterized in that hydrogen peroxide is added and brought into contact with the membrane module, and in particular, the concentration of hydrogen peroxide in the raw water is 10%.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic system diagram showing an example of a membrane separation device to which the cleaning method of the present invention is applied. This membrane separation device comprises a raw water tank 13 equipped with a raw water inflow pipe 11 and an activated carbon supply device 12, a membrane module 14 for separating a solid content (turbidity) in raw water by membrane filtration, and the membrane module 14
Hydrogen peroxide water supply device 15 provided in the previous stage and treated water tank 16 into which the treated water that has passed through the membrane module 14 flows
And a activated carbon circulating drive device 17 and a circulation line 18 for circulating the concentrated water containing activated carbon separated in the membrane module 14 into the raw water tank 13.

The normal membrane separation process is carried out by the activated carbon supply device 12
From the above, a predetermined amount of activated carbon is put into the raw water tank 13, and the circulation line 18 circulates the activated carbon-containing concentrated water. Since this membrane separation treatment can be performed in the same manner as in a conventionally-used activated carbon circulation type membrane separation device, the device configuration, processing conditions, and other detailed description will be omitted.

The hydrogen peroxide solution supply device 15 supplies hydrogen peroxide solution, that is, a mixed solution of hydrogen peroxide and water, to the raw water flowing into the membrane module 14 when the membrane module 14 is washed. The hydrogen peroxide solution can be supplied by free fall or by using a pump.

The hydrogen peroxide solution supplied from the hydrogen peroxide solution supply device 15 may be a hydrogen peroxide solution having a suitable concentration that is generally distributed, but the hydrogen peroxide solution at the position contacting the membrane module 14 may be used. Hydrogen peroxide concentration in water is 1 to 1
The range of 0% is suitable, and especially about 10% is optimal considering the cleaning effect and cost. If the hydrogen peroxide concentration during the membrane cleaning is low, it may take a long time to clean the membrane module 14 or the cleaning may not be performed sufficiently. On the contrary, the hydrogen peroxide concentration should be higher than 10%. However, it is not possible to obtain a cleaning effect suitable for the concentration.

Hydrogen peroxide added to the raw water decomposes itself to generate oxygen, and when the oxygen bubbles generated at that time burst at the surface of the membrane module 14 or the surface of activated carbon, or in the vicinity thereof, This burst energy causes vibrations in the membrane and activated carbon, and the membrane module 14 and activated carbon can be physically washed. Further, a chemical cleaning effect can be expected, in which contaminants attached to the film surface or activated carbon are removed by being decomposed and decomposed by the oxidizing power of the generated oxygen. In addition, since the decomposition of hydrogen peroxide and the oxidation reaction by the generated oxygen are exothermic reactions, a sufficient cleaning effect can be obtained even in the low water temperature period.

Furthermore, even if a large amount of hydrogen peroxide is added to and mixed with the raw water, most of it is decomposed into oxygen and water, so that treatment of cleaning waste water as when using conventional chemicals is possible. It becomes unnecessary. On the other hand, even if hydrogen peroxide remains in the treated water, its concentration becomes sufficiently low after about 30 minutes, so there is no adverse effect on the environment and there is a risk of harm to the human body. Not at all. On the contrary, a trace amount of hydrogen peroxide remaining in the treated water can provide a sterilizing effect for a long time. In addition, the hydrogen peroxide water supply device 15
Since it is not necessary to strictly control the supply amount of the hydrogen peroxide, the hydrogen peroxide solution supply device 15 can be installed at low cost and can be easily applied to existing equipment.

As described above, by periodically adding hydrogen peroxide to clean the membrane module, it is possible to set intervals for chemical cleaning of the membrane module. It is possible to reduce the cost required for cleaning, reduce damage caused by chemicals, and extend the life of the membrane module. Further, not only the membrane module but also the effect of cleaning and regenerating the activated carbon can reduce the cost required for the regeneration treatment of the activated carbon.
Moreover, the pretreatment with the addition of hydrogen peroxide also has the effect of removing biological contaminants that are the main cause of membrane clogging, and has the effect of suppressing clogging, so that the filtration efficiency in the membrane module 14 can be increased.

The position of the hydrogen peroxide solution supply device 15 is arbitrary, and it is sufficient that a predetermined amount of hydrogen peroxide can be added to the raw water in contact with the membrane module 14, in the middle of the pipe or the flow path, and in the raw water tank 13. Can be provided at any position such as
Depending on the structure of the membrane module, dipping the membrane module,
It is also possible to provide it in the stored separation tank.

[0016]

As described above, according to the method for cleaning a membrane module of the present invention, not only the cleaning of the membrane module by the hydrogen peroxide added to the raw water but also the regeneration of the powdered activated carbon by the oxygen produced by decomposition is performed. Since both can be performed at the same time, it is possible to efficiently perform both cleaning and regeneration processing. Further, cleaning with hydrogen peroxide has less adverse effect on the membrane module as compared with chemical cleaning, so that the life of the membrane module can be extended. Furthermore, it is not necessary to treat the cleaning waste water as in the case of chemical cleaning, and the impact on the environment can be reduced. Moreover, since decomposition of hydrogen peroxide and reaction of generated oxygen are exothermic reactions, sufficient cleaning effect and regeneration effect can be expected even at low water temperature. In addition, it can be carried out only by adding a simple device for supplying hydrogen peroxide solution, and does not significantly affect the facility cost.

[Brief description of drawings]

FIG. 1 is a schematic system diagram showing an example of a membrane separation device to which a cleaning method of the present invention is applied.

[Explanation of symbols]

11 ... Raw water inflow pipe, 12 ... Activated carbon supply device, 13 ... Raw water tank, 14 ... Membrane module, 15 ... Hydrogen peroxide water supply device, 16 ... Treated water tank, 17 ... Activated carbon circulation drive device, 18
… Circulation line

Claims (2)

[Claims] 1. A method for cleaning a membrane module in which raw water charged with powdered activated carbon is subjected to solid-liquid separation, wherein hydrogen peroxide is added to the raw water and brought into contact with the membrane module. Method. 2. The method for cleaning a membrane module according to claim 1, wherein the concentration of hydrogen peroxide in the raw water is 10%.