JPS63100997A - Method for sterilizing extremely pure water producing system - Google Patents

Abstract

PURPOSE:To effectively perform sterilization by passing an inorganic salt soln. through a secondary pure water producer and a circulation line for extremely pure water excepting a nonregeneration type ion exchange cartridge. CONSTITUTION:An inorganic salt soln. previously prepared in an inorganic salt tank 6 is introduced into the inlet of a secondary pure water producer 1 via a chemical feed pump 5 by opening a valve 7 provided to the upstream side of the producer 1. It is subjected to sterilizing treatment for 1-3hr. After sterilization is finished, the producer 1 is washed for 3-5hr to wash out inorganic salt. Thereby sterilization effect is extremely enhanced and it can be sterilized safely and completely.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to ultrapure water for producing ultrapure water, i.e. ultrapure water, which is used, for example, in the electronics industry, medical and pharmaceutical industry, or precision machinery industry. The present invention relates to a method for sterilizing water production systems.

[Conventional technology]

In recent years, technological innovations have been remarkable, especially in the electronics industry, and the ultrapure water used in manufacturing processes is now required to have increasingly strict water quality. For example, as shown in Table 1, the quality of ultrapure water required in the electronics industry is as close as possible to theoretically pure water, which has effectively removed impurities such as inorganic ions, as well as fine particles, bacteria (living bacteria), and organic matter. is necessary.

Table 1 Removal of impurities: Although various unit operations are combined, they can be roughly divided into ion exchange resins and reverse C' receptor i3 membranes (RO membranes) used to remove inorganic ions, and rlO membranes used to remove fine particles and bacteria. Membrane treatments such as ultrafiltration (UF), membrane filters (MF), etc. are mainly used. For example, the flow of an ultrapure water production system is shown in Figure 3, which includes pre-treatment equipment such as coagulation sedimentation 21 and sand filtration 22, and RO
23 and a regenerative hotbed ion exchange tower 24, etc., the primary water purification equipment, and further UV sterilization? It consists of a secondary pure water production device consisting of J15, non-regenerative ion exchange cartridge 16, MF or UF20, etc., and the ultrapure water is passed through the ultrapure water circulation line 4 between the secondary pure water production device and the use point 3. It is common to construct a system that circulates the water to maintain its purity at all times.

By the way, bacteria living in the ultrapure water circulation line (hereinafter referred to as the "ultrapure water system"), which includes secondary water purification equipment and use points, forms a slime layer and adheres to the walls of piping, equipment, etc. The main reason for using a hydrogen peroxide solution is that ultrapure water-based sterilization is necessary, and conventionally this sterilization was performed using a hydrogen peroxide solution. This is because it has the advantage of being able to sterilize without introducing excess salt into the line.

[Problem to be Solved by the Invention No. 1 The bactericidal action of hydrogen oxide is mainly a wound bactericidal action due to its oxidizing power. Usually used hydrogen peroxide solution; degree is 1~
5 V/V% and the infiltration time is ~3 hours. Some of the bacteria that live in ultrapure water systems are (
1) There are some bacteria that have strong catalase activity as shown in the formula, and hydrogen peroxide cannot be expected to have much of a bactericidal effect against these bacteria.

2H20□ → 2+120 + 0□ ・・・
(1) Furthermore, the slime layer that grows in the ultrapure water system and adheres to the wall surface plays the role of a protective substance against the traumatic sterilizing effects of hydrogen peroxide and the like. Therefore, in the conventional sterilization treatment of ultrapure water using hydrogen peroxide, in order to expect sufficient sterilization effect, the hydrogen peroxide solution concentration must be 5 V/V%.
It is necessary to do more than that. However, lowering the concentration of the hydrogen peroxide solution to a medium concentration is dangerous and undesirable in handling the parsley.

Moreover, since hydrogen peroxide self-decomposes, a hydrogen peroxide solution cannot be stored for a long time.

An object of the present invention is to provide a sterilization method for safely and effectively sterilizing an ultrapure water production system that produces extremely high purity water, that is, ultrapure water.

Means for Solving Problems] In order to solve the above problems, the present inventors have studied a sterilization method that is easy to handle and is particularly effective against bacteria living in ultrapure water systems. The present invention was completed after discovering that a sterilization method using inorganic salts, which had not been tried before, was the most practical.

The feature of the present invention is that a secondary pure water production device is installed for the purpose of further removing impurities in the outlet water of the primary pure water production device. Ultrapure water circulation that constantly circulates between the secondary pure water production equipment and the point of use so that a part of the outlet water (ultra pure water) of the secondary pure water production equipment is returned to the inlet of the secondary pure water production equipment. An ultrapure water production system having an ultrapure water production line, characterized in that an inorganic salt/8 solution is passed through the secondary pure water production device excluding the non-regenerating ion exchange cartridge and the ultrapure water circulation line. This is a method of sterilizing the system.

[For production]

As a result of a detailed study of the bacteria that live in ultrapure water, we confirmed that the dominant species is a bacterial group that is best suited to a low-nutrient environment, in addition to what was previously thought to be the bacterial group. These low-concentration trophic cavities are bacteria that proliferate in the presence of small amounts of organic matter, but rather do not proliferate in the presence of large amounts of organic matter, and they similarly have extremely low salt tolerance 1± to inorganic salts. I found that I was highly sensitive.

The effect of inorganic salts on bacteria of the present invention is different from the traumatic sterilization effect of conventional hydrogen peroxide, etc., and as mentioned above, it causes osmotic shock and physiological dysfunction due to salts to bacteria that have extremely low tolerance to salts. It is. In addition, inorganic salts have a sufficiently high bactericidal effect against bacteria that are difficult to kill with conventional oxidizing agent disinfectants such as hydrogen peroxide, and against bacteria that have catalase activity or bacteria that form protective substances such as slime on the outer wall of the bacterial cell. This shows that.

Various inorganic salts can be used as the inorganic salts used in the present invention, but sodium salts such as NaCl and NazSOa are preferred, and common salt is preferable.For heavy metals, it is necessary to carry out wastewater treatment of sterilized wastewater after sterilization treatment. There are some aspects that are uneconomical. Further, the concentration of the inorganic salt solution is preferably 0.1 W/V% or more, and it is also preferable to use this inorganic salt solution after membrane filtration with MF or UF with a pore size of 1 μm or less. By performing dry heat sterilization at 160°C or higher, preferably 200°C or higher, before dissolving the inorganic salts to be used and the inorganic salts, 8. Water that has been solved? By eliminating or sterilizing bacteria brought into the ultrapure water system from the 8 liquid in advance, more complete sterilization can be performed.

Further, the present invention will be explained in detail based on FIG. 1 showing one embodiment of the present invention. In the case of normal operation without sterilization treatment, a necessary amount of primary pure water is supplied to the secondary water from the primary pure water introduction pipe 2. The water that flows into the pure water production device 1 and becomes ultrapure water by the secondary pure water production device 1 passes through the use point 3 to the ultrapure water circulation line 4 where a part of it is sent to the secondary pure water production device 1. You will be returned to the entrance.

When performing sterilization treatment, open the pulp 7 provided on the upstream side of the secondary pure water production device 1, and open the inorganic salt tank 6.
The inorganic salt solution prepared above is injected into the inlet of the secondary pure water production apparatus 1 via the chemical injection pump 5. Here, the concentration of the inorganic salt solution is such that the inorganic salt concentration in the system including the secondary pure water production device 1 and the ultrapure water circulation line 4 is 0. The concentration may be determined by considering an appropriate dilution rate so that it can be maintained at IW/V% or higher.

Furthermore, in order to obtain a better bactericidal effect, preferably 0.5
It is better to carry out at W/V% or higher. However, before performing the sterilization process, the non-regenerative ion exchange cartridge must be switched to a bypass or the like to prevent it from coming into contact with the inorganic salt solution that is the sterilizing agent. That is, if a non-regenerative ion exchange cartridge comes into contact with an inorganic salt solution,
Naturally, an ion exchange reaction occurs, and the ion exchange capacity of the ion exchange resin decreases, eventually leading to breakdown.

In addition, by filtering the inorganic salt solution with MF or UPIO before injecting it into the secondary pure water production device 1, the inorganic salt solution/
The sterilizing effect can be further improved by removing bacteria and particles brought in from the liquid 8 and preventing unnecessary impurities from being brought into the ultrapure water system. Furthermore, when using table salt, for example, low-quality table salt contains halophilic bacteria, so it must be heated to 160°C before use.
As mentioned above, if you use salt that has been dry heat sterilized preferably at 200°C or higher, even low-quality salt can be easily sterilized for fine seedlings.
r; Can be made into 1M.

The sterilization time in the ultrapure water system may be about 1 to 3 hours, which is approximately the same as when using a conventional hydrogen peroxide solution. At this time, the pulp 8 in FIG. 1 may be opened to circulate in the ultrapure water system, or the pulp 9 may be opened to discharge part or all of the inorganic salt solution as a disinfectant to the outside of the system. Next, there is a cleaning step to wash out the inorganic salts that are the disinfectants remaining after the sterilization, and the cleaning time is about 3 to 5 hours.

Even when using conventional hydrogen peroxide, at least 3 hours are required, so the cleaning time of the present invention using inorganic salts is not particularly longer than the conventional method, and unlike hydrogen peroxide, inorganic salts are used. In this case, the end point of cleaning can be easily determined by measuring specific resistance or conductivity. From this point of view, it can be said that if hydrogen peroxide and inorganic salts are used together, the end point of cleaning can be easily determined even with conventional methods.

〔Example〕

Next, FIG. 2 shows a flowchart of an experimental apparatus according to an embodiment of the present invention.

To explain FIG. 2, primary pure water is supplied to the high-purity water tank 11 by 111 through the primary pure water four-person pipe 2.

The high-purity water tank 11 is sealed with N2 gas by a nitrogen gas line 13 and communicated with the atmosphere via an air filter 12.

Non-regenerative ion exchange cartridge 16.0.2 μm MF20 and ultrapure water by secondary pure water pump 14? The ultrapure water returns to the high purity water pump 11 via the 'tt ring line 4. The above experimental apparatus was operated for about one month, and then sterilized using common salt according to the present invention. First, valves 18 and 19 are closed to cut off liquid flow to non-regenerative ion exchange cartridge 16, and valve I7 is opened. Next, open the valve 7 and add the prepared 0.5 W/V% to the inorganic salt tank 6.
A saline solution is poured into a pore size of 0.45 μm (7
) The large salt solution was injected into the discharge side of the secondary pure water pump 14 via the MFIO, and the valve 9 was opened to discharge the large salt solution out of the system.

The sterilization time was about 1 hour. Similarly, after operating the experimental equipment for about one month, it was sterilized using a conventional method of IV/V% hydrogen peroxide solution. The results are summarized in Table 1. Bacteria were measured using the AST membrane filter culture method.

Table 2 As is clear from the results in Table 2, no bacteria were detected after sterilization in the present invention, but in the conventional method using hydrogen peroxide, 0.1 to 0.2 bacteria per 7 ml were measured.
Sterilization was insufficient. The reason for this is that hydrogen peroxide has little effect on bacteria that have catalase activity or bacteria that form protective substances such as slime.

〔Effect of the invention〕

As is clear from the above, the present invention uses inorganic salts that have not been conventionally used to sterilize ultrapure water, thereby achieving extremely high sterilization effects and enabling safer and more complete sterilization. becomes.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a flow showing one embodiment of the present invention, Fig. 2 is an explanatory diagram showing a flow of an experimental apparatus according to an embodiment of the present invention, and Fig. 3 is an explanatory diagram of a flow of an experimental apparatus according to an embodiment of the present invention. ! ! FIG. 2 is an explanatory diagram showing the flow of the construction system. 1... Secondary pure water cracking device, 2... Yuji pure water introduction pipe, 3
...Use point, 4...Super 1 ton water L%m line, 5...'f'! l Main bomb, 6...: Machine salt i
i Tank, 7.8.9... Valve, 10... MF or UF. 11... Pure water tank, 12... Air filter, 1
3... Nitrogen gas line, 14... Secondary pure water pump,
15... Ultraviolet sterilizer, 16... Non-regenerative ion exchange cartridge, 17, 18.19... Valve, 20
...MF, 21...coagulation sedimentation, 22...sand filtration,
23...RO124...Regenerative hotbed type ion exchange tower.

Claims (4)

[Claims] (1) In order to further remove impurities in the water at the outlet of the primary water purification equipment, a secondary water purification equipment is installed, and a part of the outlet water (ultra pure water) of the secondary water purification equipment is transferred to the secondary water purification equipment. In an ultrapure water production system having an ultrapure water circulation line that constantly circulates between the secondary water purification equipment and the point of use so as to return it to the inlet of the water purification equipment, the secondary water purification excluding non-regenerative ion exchange cartridges A method for sterilizing an ultrapure water production system, which comprises passing an inorganic salt solution through a water production device and an ultrapure water circulation line. (2) The method for sterilizing an ultrapure water production system according to claim 1, wherein the concentration of the inorganic salt solution is 0.1 W/V% or more. (3) The method for sterilizing an ultrapure water production system according to claim 1 or 2, wherein the inorganic salt solution is filtered through a membrane filter or ultrafiltration membrane with a pore size of 1 μm or less. (4) A method for sterilizing an ultrapure water production system according to any one of claims 1 to 3, wherein the inorganic salt solution is prepared by dissolving dry heat sterilized inorganic salts. .