JP2551492B2 - Sterilization method of pure water or ultrapure water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sterilization method of pure water or ultrapure water used in, for example, the electronic industry, the medical and pharmaceutical industry 8 or the precision machinery industry.

[Conventional technology]

Conventional sterilization methods for pure water production systems include a method of constantly irradiating ultraviolet rays, a method of intermittently circulating hot water, and a sterilization method using a chemical such as hydrogen peroxide or ozone.

The method of irradiating with ultraviolet rays has a small effect on bacteria resistant to ultraviolet rays, and since ultraviolet rays are constantly irradiated, resistant bacteria easily grow.

The method of circulating hot water in the system for sterilization has a drawback in that the production of pure water must be stopped during sterilization.

In the sterilization method using chemicals, not only the production of pure water must be stopped during sterilization, but also the chemicals need to be washed off after sterilization, which requires a long time for sterilization and a large amount of drainage.

Further, although the above-mentioned conventional sterilization method can sterilize vegetative cells of bacteria, spores or spores are extremely resistant as compared with vegetative cells, and therefore have little effect on spores or spores. Furthermore, some bacterial spores or spores are activated by a high temperature shock of 60 to 70 ° C for several minutes to several tens of minutes.

Therefore, the conventional sterilization method has a problem that spores or spores germinate and proliferate at an unspecified place in the system after the sterilization treatment.

[Problems to be Solved by the Invention]

As described above, the conventional sterilization methods cannot sterilize bacterial spores or spores, so that there is a risk of bacterial regrowth in the system. Therefore, the present invention, in a specific place in the pure water production system, that is, in an adsorption sterilization tower filled with an adsorbent, captures bacterial spores or spores, and germinates in the adsorption sterilization tower to convert into nutrient cells after heat treatment. The purpose is to provide a method for sterilization.

[Means for solving the problem]

In order to achieve the above-mentioned object, in the present invention, bacteria in water and bacterial spores or spores are captured by an adsorption sterilization tower filled with an adsorbent, and the captured bacteria and bacterial spores or spores germinated in the adsorption sterilization tower. The method is a method for sterilizing pure water or ultrapure water, which is characterized by sterilizing by heat treatment, and the present invention is the method described above, wherein the adsorption sterilization towers are installed in parallel in two or more, The water to be treated is passed through an adsorption sterilization tower that has been heat-sterilized in advance, and at least one of the treated adsorption sterilization towers is subjected to heat treatment by stopping the supply of the water to be treated, and then sequentially passing the water to be treated. This is a method for sterilizing pure water or ultrapure water, which is characterized by repeatedly performing heat sterilization treatment.

In the above method, as the adsorbent to be filled in the adsorption sterilization tower, an adsorbent having heat resistance and the ability to adsorb organic substances and capture bacteria and bacterial spores or spores is used.

 Hereinafter, the present invention will be described in detail.

FIG. 1 is a schematic sectional view showing an example of an apparatus used in the present invention.

In FIG. 1, an adsorption sterilization tower 5 filled with an adsorbent 4 for bacteria and bacterial spores or spores in water to be treated.
The water to be treated is passed from the feed water valve 1 to the adsorption sterilization tower 5 to obtain the treated water from the treated water valve 6.

Further, in order to sterilize the adsorption sterilization tower in which the captured bacteria and bacterial spores or spores germinated or proliferated, the feed water valve 1 and the treated water valve 6 were closed, the backwash water discharge valve 2 was opened, and heating was performed. The device 3 heats the adsorption sterilization tower.

Then, by opening the backwash water supply valve 7 and passing the sterilization-treated water in the direction opposite to the direction of water to be treated,
Dead bacteria in the adsorption sterilization tower are discharged from the backwash water discharge valve 2.

Next, backwash water supply valve 7 and backwash water discharge valve 2
Is closed, the feed water valve 1 and the treated water valve 6 are opened, and water to be treated is passed.

Similarly, the cycle of passing water to be treated, heat sterilization of the adsorption sterilization tower, and backwashing with the treated water of the adsorption sterilization tower is repeated.

Here, the adsorbent is preferably at least one selected from inorganic adsorbents such as granular activated carbon, fibrous activated carbon, zirconia, titania, and zeolite, and these adsorbents have heat resistance and are bacteria and bacterial spores. Alternatively, a substance capable of capturing spores and adsorbing an organic substance is used. The adsorbent is preferably granular activated carbon which has a high attrition strength and hardly generates fine particles.

Next, the heating device 3 is a device for heating the adsorption sterilization tower 5 to 50 to 95 ° C. for every several hours or days and holding it for several tens of minutes to several hours. ,
A method of heating by high frequency, a microwave, or the like, or a method of introducing hot water or steam separately heated into the adsorption sterilization tower and heating, and the like can be appropriately combined and used.

FIG. 2 is a schematic cross-sectional view showing an example of the apparatus of the present invention in which the adsorption sterilization towers are installed in two series in parallel.

In FIG. 2, treated water is passed through the feed water valves 1a and 1b to the adsorption sterilization tower A5a and the adsorption sterilization tower B5b, and the treated water is obtained from the treated water valves 6a and 6b. At this time the valve
2a, 2b, 7a, 7b are closed.

Then, the backwash water discharge valve 2a is opened, and the adsorption sterilization tower A5a is heat-sterilized by the heating device 3a.

Then, the backwash water supply valve 7a is opened to backwash the adsorption sterilization tower A5a with the treated water of the adsorption sterilization tower B5B.

Next, backwash water supply valve 7a and backwash water discharge valve 2a
Is closed, the feed water valve 1a and the treated water valve 6a are opened, and the water flow to the adsorption sterilization towers A and B is restarted.

Then, close the supply water valve 1b and the treated water valve 6b,
The backwash water discharge valve 2b is opened and the adsorption sterilization tower B5b is heat-sterilized by the heating device 3b.

Then, open the backwash water supply valve 7b to remove the adsorption sterilization tower A5.
The adsorption sterilization tower B5b is backwashed with the treated water from a.

Then, backwash water supply valve 7b and backwash water discharge valve 2b
Closed, open the supply water valve 1b and the treated water valve 6b,
Water flow to the adsorption sterilization tower A and the adsorption sterilization tower B is restarted.

 Similarly, a. Water flow to adsorption sterilization tower A and adsorption sterilization tower B, b. Heat sterilization of adsorption sterilization tower A c. Backwashing the adsorption sterilization tower A with the treated water of the adsorption sterilization tower B d. Water flow to adsorption sterilization tower A and adsorption sterilization tower B Heat sterilization of adsorption sterilization tower B f. The cycle of backwashing the adsorption sterilization tower B with the treated water of the adsorption sterilization tower A is repeated.

[Work]

 The pure water or ultrapure water sterilization method has the following effects.

(B) The adsorbent filled in the adsorption sterilization tower traps bacteria and bacterial spores or spores in pure water or ultrapure water and prevents them from flowing out into the treated water.

(B) In addition, a small amount of organic substances remaining in pure water or ultrapure water is adsorbed and concentrated, and the concentration of organic substances in the adsorption sterilization tower becomes higher than that in pure water or ultrapure water. Germination of spores is promoted.

Therefore, bacteria and bacterial spores or spores in pure water or ultrapure water are trapped in the adsorption sterilization tower, and high heat-resistant bacterial spores or spores are converted into nutrient cells with low heat resistance in the adsorption sterilization tower. It

In the heating device, the adsorption sterilization tower is heated to 50 to 95 ° C. and maintained for several tens of minutes to several hours to sterilize the bacterial nutrient cells in the adsorption sterilization tower.

Heat sterilization of an adsorption sterilization tower in which water to be treated is passed for several hours to several days. The interval from this heat sterilization to the next heat sterilization must be sufficiently short compared to the period in which bacteria grow and the outflow from the adsorption sterilization tower begins, and bacterial spores or spores are converted into vegetative cells. It is desirable to have time to do it.

In the pipes for maintaining and branching the adsorption sterilization towers, the water to be treated is distributed to and collected in each adsorption sterilization tower except the adsorption sterilization tower in the heat sterilization step.

The treated water of another adsorption sterilization tower is passed through the adsorption sterilization tower after heat sterilization in the direction opposite to the direction of water flow of the treated water. By this treatment, sterilized bacteria and bacterial spores or spores are discharged out of the system.

Therefore, as a whole of the pure water or ultrapure water sterilizer, treated water that is always sterilized can be obtained.

〔Example〕

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 FIG. 3 shows primary pure water obtained by treating tap water as raw water with a primary pure water producing apparatus configured with a reverse osmosis apparatus, a vacuum degassing apparatus, an ion conversion tower, a membrane filter and the like. As shown in Figure 5, adsorption sterilization tower A5a and adsorption sterilization tower B5b, ultraviolet sterilization tower 8, ion exchange resin cartridge 9, ultrafiltration device 10
Was treated with the secondary pure water producing apparatus constituted by.

The adsorption sterilization towers A and B are preheated by the heating devices 3a and 3b and kept at 80 ° C for 1 hour for sterilization treatment, and primary pure water is passed to the adsorption sterilization towers A and B at 50 / h respectively. Then, it was treated with an ultraviolet sterilization tower, an ion exchange cartridge and an ultrafiltration device to obtain ultrapure water.

After passing the primary pure water through the adsorption sterilization tower for 24 hours, the amount of water passing through the adsorption sterilization tower B was set to 100 / h and the passage of the primary pure water through the adsorption sterilization tower A was stopped. The adsorption sterilization tower A whose water flow was stopped was heated by the heating device 3a and heated to 80 ° C. The heating pattern at this time was such that the temperature was raised in 45 minutes and kept at 80 ° C. for 1 hour, then a part of the treated water in the adsorption sterilization tower B was introduced into the lower part of the adsorption sterilization tower A to carry out backwashing. The temperature was lowered in minutes.

After the sterilization treatment of the adsorption sterilization tower A, primary pure water was passed through the adsorption sterilization tower A at 50 / h, and the water flow rate to the adsorption sterilization tower B was set at 50 / h.

In the adsorption sterilization tower B, primary pure water was passed for 48 hours after the start of water flow, that is, for 24 hours after the start of the sterilization treatment of the adsorption sterilization tower A, and then heat sterilization was performed under the same conditions as the heat sterilization.

Then, the adsorption sterilization towers A and B were repeatedly passed through the primary pure water and sterilized at intervals of 48 hours. The viable bacteria in the secondary pure water after about one month were measured.

According to JIS K0550 (1988), this was cultivated for 5 days at a culturing temperature of 25 ° C. using an M-TGE medium, and the formed colonies were counted to determine the viable cell count.

 The results are shown in Table 1-I.

Comparative column 1 Using the same apparatus as in the above-mentioned example, the primary pure water was passed through the adsorption sterilization tower at intervals of 168 hours and the heat sterilization under the above heating conditions was repeated.

The number of viable bacteria in ultrapure water after about 1 month is shown in Table 1-II.

Comparative Example 2 The primary pure water was treated in a secondary pure water producing apparatus composed only of an ultraviolet sterilization tower, an ion exchange resin cartridge and an ultrafiltration device without passing through the adsorption sterilization tower. The number of viable bacteria in the secondary pure water after about 1 month is shown in Table 1-III.

[Effects of the Invention] As described above, according to the method of the present invention, bacteria and bacterial spores or spores in pure water or ultrapure water can be effectively sterilized, and viable bacteria in pure water or ultrapure water can be significantly reduced. I was able to.

Further, by installing two or more adsorption sterilization towers in parallel, it was possible to obtain treated water that was always sterilized without stopping water flow.

[Brief description of drawings]

1 and 2 are schematic cross-sectional views showing an example of an apparatus used in the present invention, and FIG. 3 is a schematic process diagram of a secondary pure water producing apparatus incorporating the method of the present invention. 1,1a, 1b …… Supply water valve, 2,2b, 2b …… Backwash water discharge valve, 3,3a, 3b …… Heating device, 4,4a, 4b …… Adsorbent, 5,5a, 5b… … Adsorption sterilization tower, 6,6a, 6b …… Treatment water valve, 7,7a, 7b …… Backwash water supply valve, 8 …… Ultraviolet sterilization tower, 9 …… Ion exchange resin cartridge, 10 …… Ultrafiltration apparatus

Continued Front Page (72) Ken Nakajima Ken 2 1-2-1, Fujisawa, Kanagawa Prefecture Ebara Research Institute Ltd. (72) Inventor Hiroyuki Shima 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Stock Company EBARA MFG. (72) Inventor Manabu Tsujimura 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Stock company EBARA MFG. (56) Reference JP-A-49-70450 (JP, A) JP-A-64-51189 JP, A)

Claims (2)

(57) [Claims] 1. Bacteria and bacterial spores or spores in water are captured by an adsorption sterilization tower filled with an adsorbent, and the captured bacteria and bacterial spores or spores germinated in the adsorption sterilization tower are sterilized by heat treatment. A method for sterilizing pure water or ultrapure water, characterized by: 2. The adsorption sterilization towers are installed in parallel with each other, and the water to be treated is passed through the adsorption sterilization tower which has been heat-sterilized in advance, and at least one of the treated adsorption sterilization towers is Stop the supply of water to be treated and perform heat treatment,
The method of sterilizing pure water or ultrapure water according to claim 1, wherein the water to be treated and the heat sterilization treatment are sequentially repeated.