JP2000157850A - Separating membrane preservation liquid and separating membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the high sterilization effect for a long period of time and prevent the deterioration of a separating membrane and the permeation performance thereof by preparing a separating membrane preservation liquid from a solution containing sodium bisulfite. SOLUTION: A separating membrane preservation liquid in the wet state used for preserving a separating membrane for separating permeated water by filling a raw water used in the fields of food industry, medical care, purification of water and the like when being not used in prepared from a solution containing sodium sulfite. The sodium sulfite is provided with the high sterilization effect for aerobic bacteria, free from toxicity, keeping its sterilization effect for a long time and not oxidizing a polymer nor deteriorating the separating membrane, by which the permeation performance is not lowered. The concentration of the sodium bisulfite to be used is preferably in the range of 0.01-5%, more preferably 0.02-0.05%. Although no particular restrictions are applied for a solvent, water is best for the purpose in consideration of operation properties, and among other things, sterilized water is preferred most.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a separation membrane preservation solution and a separation membrane module.

[0002]

2. Description of the Related Art In the fields of food industry, medical treatment, water purification and the like, separation membranes are used for filtering raw water to obtain permeated water. There are various types of separation membranes such as microfiltration membranes, ultrafiltration membranes, and reverse osmosis membranes, which can be used depending on the application. They are classified into a tubular type, a hollow fiber type, a flat membrane type and the like according to the shape, and these are used in a state of being housed in a separation membrane module.

[0003] In order to maintain performance, the separation membrane must be stored in a wet state even when not in use. However, when stored in a wet state, bacteria proliferate on the surface of the separation membrane or in the module, and on the contrary, the performance deteriorates. Therefore, when not used, the module is usually stored in a state where the separation membrane storage solution is filled in the module. Conventional separation membrane storage solutions include aqueous solutions containing components such as formaldehyde, sodium hypochlorite, or hydrogen peroxide.

[0004]

However, an aqueous solution containing formaldehyde has a high bactericidal effect but is very toxic. Therefore, the separation membrane module must be sufficiently washed before use, which is troublesome. Further, when washing is performed, a large amount of wastewater is generated, which makes it difficult to treat the wastewater.

In the case of an aqueous solution containing sodium hypochlorite or hydrogen peroxide, there is a drawback that the sterilizing effect decreases with time. In addition, since these generate gas, there is a fear that liquid may overflow when the separation membrane module is opened. A polymer such as polysulfone is usually used as a material for the separation membrane. However, since sodium hypochlorite and hydrogen peroxide oxidize the polymer material, the separation membrane is deteriorated and the permeability is reduced.

Therefore, the present invention provides a separation membrane preservation solution which has no toxicity, maintains a high sterilizing effect for a long period of time, and does not cause deterioration of the separation membrane and deterioration of permeation performance, and a separation membrane module filled with the same. It is intended to provide.

[0007]

The preservation solution for a separation membrane of the present invention is characterized by comprising a solution containing sodium bisulfite. Further, the separation membrane module of the present invention is characterized in that the separation membrane storage solution is filled.

[0008] Sodium bisulfite, a component of the separation membrane preservation solution of the present invention, has a high bactericidal action against aerobic bacteria. In addition, it has no toxicity, maintains a bactericidal effect for a long period of time, and does not oxidize the polymer, so that it does not deteriorate the separation membrane and therefore does not lower the permeation performance. In addition, in the separation membrane module filled with this, there is no fear of damaging the human body, the growth of bacteria is suppressed for a long time, and the deterioration of the separation membrane and the deterioration of the permeation performance are not caused. The preservation solution for a separation membrane of the present invention has a bactericidal effect only on aerobic bacteria, and has no bactericidal effect on anaerobic bacteria. However, bacteria that enter during the production process or storage of the separation membrane module are usually aerobic bacteria, and thus anaerobic bacteria need not be taken into account.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the separation membrane preservation solution of the present invention,
The preferred concentration of sodium bisulfite is 0.01-5%, more preferred concentration is 0.02-0.05%. The solvent is not particularly limited, but water is best in consideration of operability. Among them, sterile water is preferable.

[0010] The separation membrane preservation solution of the present invention comprises a
It is applicable regardless of the shape, and there is no limitation on the material of the separation membrane. The method for using the preservation solution for a separation membrane of the present invention is the same as the conventional one, and there is no particular limitation. The most common method is to fill the separation membrane preservation solution of the present invention into a module and immerse the separation membrane, but it is also possible to simply apply the separation membrane preservation solution to the membrane surface.

[0011]

EXAMPLES Example 1 A preservation solution for a separation membrane consisting of an aqueous solution containing 5% of sodium bisulfite was subjected to the following tests. First, a module accommodating a hollow fiber type separation membrane made of polysulfone was prepared, and the storage solution was filled therein, whereby the separation membrane was immersed. Next, 8 days and 30 days after the immersion, the separation membrane preservation solution was removed, and the raw water (type: sterile pure water, amount:
80 l / min) was filtered at a differential pressure of 1.0 kgf / cm ² , and the amount of the obtained permeated water was measured. Subsequently, after culturing a predetermined amount of permeated water under a certain condition, the number of viable bacteria contained in the permeated water was measured. At the same time, the tensile strength and elongation of the hollow fiber membrane, the weight of the packing (made of acrylonitrile butadiene rubber), and the hardness of the casting resin (epoxy resin) were measured. Then, these measurement results were compared with the results (initial values) before filling with the separation membrane storage solution. Table 1 shows the results.

[0012] A similar test was conducted on a separation membrane preservation solution consisting of an aqueous solution containing 5% of sodium hypochlorite.
Table 2 shows the results.

[0013]

[Table 1] ---------------------------------------------- ---------------- initial value 8 days after 30 days after ------ ------ -------- permeate flow ^{(m 3} / ^{m 2} h) 0.82 0.81 0.82 number of living bacteria (CFU / ml) 0.0 0.0 0.0 tensile strength ^{(kgf / cm 2) 29.0 28.5} 28.6 elongation (%) 38.0 38.0 37.8 packing weight (g) 0.32 0.32 0.31 casting resin hardness (JIS- A) 99 or more 99 or more 99 or more ------------------------------------------ --------------------

[0014]

[Table 2] ---------------------------------------------- ---------------- initial value 8 days after 30 days after ------ ------ -------- permeate flow ^{(m 3} / ^{m 2} h) 0.80 0.78 0.77 number of living bacteria (CFU / ml) 0.0 0.4 0.7 tensile strength ^{(kgf / cm 2) 29.0 28.0} 26.0 elongation (%) 38.0 34.0 27.0 packing weight (g) 0.32 0.32 0.32 casting resin hardness (JIS- A) 99 or more 99 or more 99 or more ------------------------------------------ --------------------

[0015] As shown in Table 2, in the separation membrane preservation solution containing sodium hypochlorite, the number of viable bacteria increased with the elapse of time, and the deterioration of the separation membrane and the decrease in permeation performance were observed. . On the other hand, in the case of the separation membrane preservation solution containing sodium bisulfite, as shown in Table 1, in all items, the measurement results after 30 days were almost the same as the initial values. From the above, the separation membrane storage solution of the present invention,
It was confirmed that the high sterilizing effect was maintained for a long period of time, and did not cause the deterioration of the separation membrane and the decrease in the permeation performance.

Example 2 The concentration of sodium bisulfite was 0.01, 0.02, 0.
Aqueous solutions of 05, 0.5, 5, and 10% were prepared and tested in the same manner as in Example 1. However, the measurement was performed only 30 days after immersion. Table 3 shows the results.

[0017]

[Table 3] ---------------------------------------------- ------------------------ 0.01% 0.02% 0.05% 0.5% 5% 10% ----- ----- ---- - ----- ---- ---- permeate flow ^{(m 3 / m 2 h)} 0.80 0.82 0.81 0.80 0.82 0.80 number of living bacteria (CFU / ml) 0.1 0.0 0.0 0.0 0.0 0.0 tensile strength (kgf / cm ² ) 28.3 28.6 28.6 28.5 28.6 28.0 Elongation (%) 38.0 38.1 38.0 38.0 37.8 37.8 Packing weight (g) 0.31 0.32 0.31 0.31 0.31 0.31 Mold resin hardness (JIS-A) 99 or more 99 or more 99 or more 99 or more 99 that's all ------------------------------------------------- ---------------------

From the results shown in Table 3, the preferred concentration of sodium bisulfite is 0.01 to 5%, especially 0.02 to 5%.
0.05% was found to be optimal.

[0019]

The separation membrane preservation solution of the present invention has no toxicity, maintains a high bactericidal effect for a long period of time, and does not cause deterioration of the separation membrane and deterioration of the permeation performance. Therefore, in the separation membrane module filled with this, there is no fear of damaging the human body, the growth of bacteria is suppressed for a long time, and the deterioration of the separation membrane and the deterioration of the permeation performance are not caused.

Continuation of the front page F term (reference) 4D006 GA03 GA06 GA07 HA01 KC21 KD30 KE05P KE06P LA01 MA01 MB16 MB18 MC62X PA01 PB02 PC11 PC41

Claims (4)

[Claims] 1. A preservation solution for a separation membrane, comprising a solution containing sodium bisulfite. 2. The method according to claim 1, wherein the concentration of sodium bisulfite is 0.01 to
The preservation solution for a separation membrane according to claim 1, which is 5%. 3. The method according to claim 1, wherein the concentration of sodium bisulfite is 0.02 to 0.02.
The preservation solution for a separation membrane according to claim 1, which is 0.05%. 4. A separation membrane module filled with the separation membrane preservation solution according to any one of claims 1 to 3.