JPH0630765B2 - Aseptic pure water supply method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to aseptic pure water in the field of using high-purity pure water, such as the electronics industry, chemical industry, precision parts industry, and food industry. Is always about how to supply.

[Problems to be Solved by Prior Art and Invention]

In recent years, high-purity water is required for pure water used in manufacturing processes such as the electronics industry, chemical industry, precision parts industry, food industry, etc. that use pure water, and cleaning processes.
Moreover, it is always required to be sterile pure water. However, in the pure water production / supply system in these fields, pure water produced by one device is used for various purposes. For example, in the chemical industry, there is a tendency to increase in size and complexity because it is used for preparation, cleaning, preparation, and dilution. Especially if the existing equipment is modified or added.

In a pure water production and supply system that is becoming larger and more complex in this way, a large number of tanks, valves, pumps, filters, and long-distance pipes are used and installed, creating an environment in which live bacteria can easily propagate. providing. Also, in the pure water supply line, the number of branch pipes is increased, and a portion where pure water is hard to flow and flows, that is, a so-called pool is easily formed, and live bacteria are easily propagated there. In particular, when the operation is stopped, pure water does not flow, and the whole is pooled so that live bacteria can easily propagate. Therefore, as a countermeasure, a circulation line that returns pure water to the pure water tank of the pure water production device is installed between the pure water production device and each point of use (where pure water is distributed and supplied to the site of use). In some cases, there is no retention part through a constant circulating flow of water so as to suppress the generation of viable bacteria, or a re-filtration system is individually provided at each use point.

Furthermore, the pure water supply line must be sterilized regularly. As a conventional general sterilization operation, 1 to 3% by weight
Treatment with an aqueous solution of hydrogen peroxide for 1 hour, or 1-5ppm
Treatment with an aqueous solution of sodium hypochlorite for 1 hour is used. In such a method, a large amount of waste liquid is discharged at the time of sterilization, and it is necessary to dispose of it, and strong oxidizers such as hydrogen peroxide and sodium hypochlorite cannot be removed from the ion exchange resin / membrane in the pure water production equipment. There is also a possibility that the filters will be decomposed by oxidation. In addition, there is a drawback that the sterilizing agent must be discharged by washing the inside of the system with a large amount of pure water at the end of sterilization.

Other methods such as steam sterilization and hot water sterilization are not very economical methods considering their energy efficiency.

Due to these factors, in the process of becoming larger and more complex,
Even from a large and complicated pure water production and supply system,
A great deal of energy, cost, labor, and time were required to constantly supply sterile pure water.

The present invention is a system for producing and supplying high-purity water,
It is an object of the present invention to solve many problems of sterilization by the conventional method as described above, and to provide a method which can always supply sterile pure water even in an apparatus which is easy to operate and which is large and complicated.

[Means for Solving the Problems]

The present inventor has conducted various studies to achieve the above object.

Fluorine compounds have long been used as dental caries preventives and wood preservatives, and are known to exhibit specific activity against the living body. Based on these findings, for live bacteria that can grow in pure water, such as Pseudomonas spp. Or fungi,
As a result of detailed examination of the effect of various water-soluble compound components present in pure water on bacterial growth, the compound concentration was examined,
It has been found that the presence of a trace amount of fluoride ions in pure water has a surprising bactericidal effect. That is, even if the concentration of fluoride ions present in pure water is maintained at a low level of 10 ppm or less, the viable bacteria die, and even at a low level of 1 ppm or less, a viable bacteriostatic state in which viable bacteria do not grow can be obtained. It was revealed. The sterilization mechanism of such trace amount of fluoride ion is not clear, but it is presumed that it showed a unique physiological effect of fluoride ion, which is different from general sterilization ability using hydrogen ion concentration (pH) and redox. It

Furthermore, the concentration of fluorine ions effective in preventing the growth of viable bacteria in pure water varies depending on the type of compound used to give the fluorine ions, and in hydrofluoric acid (HF), 0.1 ppm or more, preferably 0.1 to While effective at a concentration of 100 ppm, it has been found that water soluble fluoride salts, such as alkali metal fluorides or ammonium fluoride, are effective at concentrations of 1 ppm or greater, preferably 1-100 ppm. However, if the concentration is substantially higher than 100 ppm, the sterilizing effect can be obtained, but in some cases it cannot be said as pure water, and it takes time and effort to sufficiently remove the fluorinated compound.

Therefore, according to the first aspect of the present invention, hydrofluoric acid having a concentration of 0.1 to 100 ppm is present in the pure water supplied in the pure water supply line, and thus the viable bacteria are produced by the fluorine ions present in the pure water. There is provided a method for supplying aseptic pure water, characterized in that pure water is supplied while being kept aseptic without being propagated.

Further, according to the second aspect of the present invention, the water-soluble fluoride salt having a concentration of 1 to 100 ppm is present in the pure water supplied in the pure water supply line, and thus it is generated by the fluorine ions present in the pure water. Provided is a method for supplying aseptic pure water, which is characterized in that pure water is supplied while keeping the sterilized state without propagating bacteria.

The sterile pure water supplied by the above-described method of the present invention can be used for applications in which the presence of a trace amount of a fluorinated compound contained in the pure water is acceptable. If desired, the fluorinated compound can also be completely removed before use, for example with an ion exchange resin. In the method of the present invention, hydrofluoric acid or a fluoride salt is added to pure water in the form of an aqueous solution thereof to be present in pure water, and the addition point is attached to the pure water production / supply system. It may be a pure water supply line, particularly any suitable position on the pure water supply pipe. Further, the water solubility of a water-soluble fluoride salt means that it has a solubility that can be dissolved in water at a concentration of 1 to 100 ppm, and examples of suitable fluoride salts include alkali metals such as sodium and potassium. , Lithium fluoride, alkaline earth metals such as calcium, magnesium fluoride, ammonium fluoride, iron or other suitable metal fluorides, and the like.

Below, tests were carried out in order to investigate the bactericidal or bacteriostatic action of various compounds used at extremely low concentrations of 1 to 100 ppm.
That is, various compounds are added to a 1000-fold diluted solution of normal agar liquid medium to prepare a test solution having a predetermined compound concentration. An appropriate amount of viable bacteria isolated from pure water collected by passing a pure water sample sampled from a pure water producing device through a microporous membrane was added to the test solution (the initial viable cell inoculum count was 5 × 10 ⁴ cells / ml). Yes) 4 days 3
After static culture at 0 ° C., the viable cell count after breeding was measured by the MF method (viable cell count measurement method according to JIS K0101).

The measured live cell counts are summarized in Table 1 below.

In Table 1 above, those showing a bactericidal effect are indicated by +, those showing proliferation are indicated by a-, and those showing a bacteriostatic effect are indicated by ±. According to this, the bactericidal effect of HF is clear. However, even if HCl was added at a concentration of 10 ppm, no bactericidal effect was found, and it can be seen that the sterilizing action of HF is specific to fluoride ions, not merely due to pH fluctuation. Further, it can be seen that even a fluoride salt has a bactericidal effect depending on the added amount. Similarly, in the case of salt, no bactericidal effect was found even when NaCl was added at a concentration of 100 ppm, and it is therefore due to the fluoride ion generated from the fluoride salt.

Table 1 shows the bactericidal or bacteriostatic action of 100 ppm hydrofluoric acid and 50 to 100 ppm of water-soluble fluoride salt. In this test, the behavior of viable bacteria was determined by using a 1000-fold dilution of ordinary agar liquid medium. Therefore, it can be said that the bactericidal or bacteriostatic action was investigated in an environment in which live bacteria are prone to propagate. Therefore, since pure water contains almost no substance that serves as a nutrient source for viable bacteria, hydrofluoric acid and water-soluble fluoride salts have sufficient sterilizing or bacteriostatic effects in pure water even at lower concentrations. The present inventors have found that hydrofluoric acid is effective at 0.1 to 100 ppm and water-soluble fluoride salt is effective at 1 to 100 ppm.

The present invention will be specifically described below with reference to FIG. 1 of the accompanying drawings showing a pure water production / supply system to which the method of the present invention is applied.

FIG. 1 is a schematic view of a system including a pure water supply line showing an example of an apparatus to which the method of the present invention is applied. In these figures, raw water is passed through a pretreatment device 2, a reverse osmosis membrane device 3, a two-bed three-column type ion exchange device 4, an ultraviolet sterilization device 5, and a reverse osmosis membrane device 3 ′ installed in a pure water producing device 1. It is purified into primary pure water, and the primary pure water is stored in the primary pure water storage tank 6. Then, in order to obtain pure water of higher purity, the final high-purity water is passed through a cartridge type polisher (ion exchange resin device) 7, an ultraviolet sterilizer 5 ', a membrane filter 8 and an ultrafiltration membrane device 9. The high-purity water is sent to each use point 11 through the pure water supply line 10. The return line 13 is returned from an appropriate portion of the pure water supply line pipe 10, and the pure water is branched and returned to the pure water storage tank 6.

In the first aspect of the present invention, an aqueous solution of hydrofluoric acid is provided so that the fluorine ion concentration in the pure water after a suitable position in the pure water supply line pipe, that is, in the pure water supply line pipe is 0.1 to 100 ppm. Is intermittently or continuously injected from the injection pipe 12 at an appropriate point of the pure water supply line 10 using, for example, a chemical injection pump, and uniformly mixed so that the fluorine ion concentration in pure water is always constant. To do. The amount of fluoride ions to be present in pure water may be adjusted depending on factors such as bacterial species generated in the system, concentration of bacteria, temperature and residence time.
Even if added in excess of 0 ppm, it may have an effect on corrosion of equipment materials. Also, if it is less than 0.1 ppm, the bactericidal effect becomes weak.

In the second aspect of the present invention, instead of hydrofluoric acid, a salt of hydrofluoric acid (fluoride salt), for example, an aqueous solution of NH ₄ F, NaF, KF or the like is added to adjust the concentration of these salts to 1 to 100 ppm. To be injected.

At each use point, if there is no problem even if a small amount of fluorine ion exists, use it as it is. If fluorine ion is inconvenient for the purpose of using pure water, use it as No. 3 use in Fig. 1. A polisher 14 or the like filled with an ion exchange resin may be installed and water may be passed through this to remove fluorine ions, and then used. Further, in the embodiment, the aqueous solution of hydrofluoric acid or its salt is directly injected into the pure water in the outlet pipe of the pure water producing apparatus, but once the storage tank is provided, it is supplied to the point of use by pumping or pumping. You can also do it.

In the present invention, a sterilizing effect and a bacteriostatic effect are produced only by allowing a small amount of fluorine ions to exist in pure water during the pure water production / supply system, for example, via a chemical injection pump, etc. Even in the apparatus, pure water in a sterile state can be constantly supplied.

Next, the present invention will be described based on the following examples and comparative examples.

Example 1 A pure water production / supply system of 4 m ³ / h having the pure water supply line shown in FIG. 1 was operated under the following conditions.

Initial sterilization by conventional method: To make 1% H ₂ O ₂ aqueous solution in the primary pure water storage tank 6 35
The% H ₂ O ₂ aqueous solution was added to the primary pure water for adjustment.

After removing the connecting conduits on the inlet side and the outlet side of the cartridge type polisher (ion exchange resin device) 7 from the polisher and directly connecting the two, thereby forming a bypass connection part that does not pass through the polisher 7, a circle line and a youth 1% H ₂ O ₂ from storage tank 6 to pure water supply line 10 to the point
Drain was performed at each use point No. 1, 2, 4 and 5 while sending the solution. After the above operation was carried out for 1 hour, the H ₂ O ₂ solution was retained in the line for an additional 1 hour to immerse the inner wall surface of the line. Then, each line was washed with pure water, the H ₂ O ₂ solution was discharged, and it was confirmed that the specific resistance of water was 17.5 MΩ · cm and the number of viable cells was 0/100 ml at the No. 1 point of use.

Bacteria count frequency and method: Restart the production and supply of pure water, and once every 5 days, sample the pure water sample from the No. 1 point of use and perform sampling to determine the viable cell count per 100 ml of pure water. The water sample was measured by the viable cell count method (JIS K0101) using the membrane filter method.

Operation method for pure water production and method for practicing the present invention: After the above initial sterilization, 4 m ³ is stored in the primary pure water storage tank 6.
The primary pure water is supplied at a rate of / h.

In addition, primary pure water from the primary pure storage tank was passed through a cartridge type polisher (cartridge type mixed bed ion exchange resin device), an ultraviolet sterilizer, a membrane filter and an ultrafiltration membrane at 8 m ³ / h to purify the purified water. Use high-purity pure water. Returning to the high-purity pure water primary pure water storage tank again about 4m ³ / h in the high purity deionized water at about 4m ³ / h is fed to use point through the pure water supply line 10.

In this embodiment, the pure water supply line 10 to the point of use is used.
Then, at a position subsequent to the connection point of the branch pipe 13 of the line returning to the primary pure water storage tank, for example, a hydrofluoric acid aqueous solution is chemically injected from the injection pipe 12 so that the fluorine ion concentration in the high-purity pure water becomes 1 ppm. Water in line 10 was continuously injected via a pump.

After the above-mentioned initial sterilization, the pure water production and supply were continued in the same manner as above, and the fluoride ion was also replenished. Was measured by the method. The resulting viable cell count is shown in FIG. 2 of the accompanying drawings. Aseptic pure water could be supplied for 90 days or more at the No. 1 point of use.

Comparative Example 1 The same initial sterilization and pure water production and supply operations as in Example 1 were performed, but the injection of HF was omitted.

With respect to the pure water sample sampled from the use point No. 1, the viable cell count was measured in the same manner as in Example 1, and the result is shown in FIG. After the initial sterilization, live bacteria were confirmed on the 5th day,
After that, it increased remarkably.

Example 2 After the same initial sterilization as in Example 1, an aqueous hydrofluoric acid solution was replenished in the same manner as in Example 1 so that the hydrogen fluoride concentration in the pure water in the supply line 10 was maintained at 100 ppm.

Aseptic pure water could be supplied at the No. 1 point of use over 90 days after the initial sterilization.

Example 3 In the supply line 10, the concentration of ammonium fluoride in pure water was 50.
The method of Example 1 was repeated by injecting an ammonium fluoride aqueous solution so that the concentration would be ppm.

Fig. 4 shows the results of measuring the viable cell count of the pure water sample extracted at No. 1 point of use. Aseptic pure water could be supplied for 90 days or more after the initial sterilization.

Example 4 Sodium fluoride concentration in pure water was 50 pp in the supply line 10.
The method of Example 1 was repeated by injecting an aqueous NaF solution so as to obtain m.

Fig. 5 shows the result of measuring the viable cell count of the pure water sample extracted at No. 1 point of use. Aseptic pure water could be supplied for more than 90 days.

Example 5 The method of Example 1 was repeated by injecting an aqueous solution of hydrofluoric acid into the supply line 10 so that the concentration of hydrogen fluoride in pure water was 0.1 ppm.

Fig. 6 shows the result of measuring the viable cell count of the pure water sample extracted at No. 1 point of use. Aseptic pure water could be supplied for 90 days or more after the initial sterilization.

Example 6 In the supply line 10, the concentration of ammonium fluoride in pure water was 1
The method of Example 1 was repeated by injecting an ammonium fluoride aqueous solution so that the concentration would be ppm.

Fig. 7 shows the result of measuring the viable cell count of the pure water sample extracted at No. 1 point of use. Aseptic pure water could be supplied for 90 days or more after the initial sterilization.

Example 7 The sodium fluoride concentration in pure water in the supply line 10 was 1 pp.
The method of Example 1 was repeated by injecting an aqueous NaF solution so as to obtain m.

Fig. 8 shows the result of measuring the viable cell count of the pure water sample extracted at No. 1 point of use. Aseptic pure water could be supplied for more than 90 days.

[Brief description of drawings]

FIG. 1 is a flow diagram of a pure water production / supply system having a pure water supply line to which the method of the present invention can be applied. 2, FIG. 4 to FIG. 7 and FIG. 8 are curves respectively showing the changes with time of the viable cell count in the aseptic pure water supplied in Examples 1, 3 to 6 and 7 of the present invention. FIG. 3 is a curve diagram showing the change with time of the viable cell count (logarithmic display) in the pure water supplied, which was obtained in Comparative Example 1 in which the present invention was not performed.

Front page continuation (72) Inventor Kaji Ota 2-1-1 Otemachi, Chiyoda-ku, Tokyo Nomura Micro Science Co., Ltd. (72) Inventor Koichi Sawada 2-1-1 Otemachi, Chiyoda-ku, Tokyo Nomura Micro Science Co., Ltd. (56) Reference JP-A 63-221889 (JP, A) JP-A 50-125548 (JP, A) JP-A 57-15885 (JP, A)

Claims (2)

[Claims] 1. A pure water supplied in a pure water supply line is allowed to contain hydrofluoric acid at a concentration of 0.1 to 100 ppm, and the viable bacteria are not propagated by the fluorine ions thus existing in the pure water. A method for supplying aseptic pure water, characterized in that pure water is supplied while being kept sterile. 2. A water-soluble fluoride salt having a concentration of 1 to 100 ppm is present in pure water supplied in the pure water supply line,
A method for supplying aseptic pure water, characterized in that pure water is supplied while keeping the sterilized state without allowing viable bacteria to propagate by the fluorine ions present in the pure water.