JPS60261585A - Manufacture of extremely pure water - Google Patents

Abstract

PURPOSE:To remove bacteria almost completely by heating water to be treated in whole or in part in a treating system when demineralized water is produced by a combination of various operations. CONSTITUTION:When demineralized water is produced by a combination of unit operations such as reverse osmosis, ion exchange, ultrafiltration, precision filtration, and ultraviolet sterilization, the temp. of water to be treated is kept at 70-110 deg.C in part or in whole in a treating system. Bacteria can be removed almost completely in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ultrapure water, and more specifically, the present invention relates to a method for producing ultrapure water. The present invention relates to a method for producing ultrapure water by inhibiting.

Reverse osmosis, ion exchange, ultrafiltration, precision filtration, etc. are known methods for producing pure water, and these methods can be used alone or in combination of two or more methods. This allows us to obtain pure water with a purity level that suits the purpose of use. There is also a method in which ultraviolet sterilization treatment is applied during the production process of purified pure water to sterilize and remove viable bacteria that are difficult to remove with the physical treatment described above.For example, Figure 1 shows a representative example of pure water. This is a flow diagram illustrating the targeted production method, and is configured by connecting a primary pure water system and a secondary pure water system in series.In other words, in the primary pure water system, a flocculant and an auxiliary agent are added to raw water. In addition, the treated water is pretreated to remove suspended matter, and then an acid is added to the treated water, followed by decarboxylation. After being stored in a storage tank, it is sent to a reverse osmosis device through a heat exchanger and a filter. The optimum temperature is 15~
Since the temperature is about 30℃, the treated water before reverse osmosis treatment is heated or cooled by passing it through a heat exchange device as described above, and the temperature of the treated water is adjusted to the above optimum temperature before being sent to the reverse osmosis device. I have to. The permeated water that has undergone reverse osmosis is sent to an ion exchange device via a storage tank, and after ions are removed, it is sent to the storage tank through a filter to complete the treatment of the primary pure water system. The storage tank is sealed with nitrogen gas to prevent air from entering.

The treated water that has completed the primary water purification treatment is then sent to the secondary water purification system, where it is sterilized by an ultraviolet sterilizer, and then sent to an ultrafiltration device via a cartridge polysha, and some of it is sent to the ultraviolet sterilizer. The waste is returned to the storage tank in front of it, and a portion is sent to the point of use through a filter. Through this series of treatments, most of the impurities in the raw water are removed and the water can be used as ultrapure water.

By the way, the quality of ultrapure water is evaluated based on resistivity, amount of fine particles, number of viable bacteria, amount of organic matter, etc.

Among these, the number of viable bacteria is measured as a type of fine particle, but it is important in evaluating the quality of ultrapure water because viable bacteria has the ability to self-propagate and can increase abnormally if growth conditions are met. occupying a position of power.

However, although the method for producing ultrapure water as described above can almost completely remove solid suspended matter and ions,
It is not always possible to remove viable bacteria sufficiently. In other words, it is impossible to completely remove microscopic viable bacteria in water by ion exchange or ultrafiltration, and even with ultraviolet sterilization treatment as explained in Figure 1, viable bacteria cannot be completely removed. can only be effective to the extent of suppressing the proliferation of bacteria, and a complete bactericidal effect cannot be expected. As a result, there is a risk that a small amount of viable bacteria remaining in the ultrapure water will proliferate in the dead space, leading to a decline in quality.Also, in the ultrapure water manufacturing process, water quality often deteriorates due to back contamination from the point of use. has been experienced.

The present inventors have focused on these circumstances and have conducted various studies with a particular focus on complete removal of viable bacteria.

As a result, in the ultrapure water manufacturing process, the treated water is heated to a temperature of 70 to 110℃.
It was discovered that heating to a certain temperature could eradicate viable bacteria, and this led to the completion of the present invention.

That is, the configuration of the ultrapure water production method according to the present invention includes reverse osmosis,
In a method for producing pure water using unit operations such as ion exchange, ultrafiltration, microfiltration, and ultraviolet sterilization, either singly or in combination, the temperature of the treated water in part or the entire treatment system is maintained at 70 to 10°C. However, there is a gist.

In the present invention, a heater or heat exchanger is installed in the ultrapure water production line or storage tank to maintain the water temperature at 70 to 110°C, and this heating almost completely kills living bacteria in the water. Deterioration in the quality of ultrapure water due to contamination or proliferation of viable bacteria can be almost completely prevented. For example, in Figure 2, a heater is installed in place of the ultraviolet sterilizer in the secondary pure water system in the known pure water production process shown in Figure 1, and the water temperature is kept at 70 -
This is an example flow of the present invention in which the temperature can be increased to 110°C. With this configuration, the temperature of the treated water at each position of the cartridge polisher, ultrafiltration device, and filter arranged downstream of the heater. can be raised to any temperature. Therefore, the water temperature can be adjusted to 70 to 110 by using this heater.
If the temperature is raised to ℃, it is possible not only to sterilize the cartridge cartridge, which tends to be a breeding ground for microorganisms, but also to almost completely eradicate viable bacteria in the treated water. Furthermore, dead bacteria are almost completely removed in the ultrafiltration process, and the temperature of the treated water that passes through the filter from the ultrafiltration device is also maintained at a high temperature, preventing back contamination by live bacteria from the point of use. This does not occur at all, and ultra-high purity water can be obtained. By the way, the heating temperature of the treated water must be 70°C or higher, preferably 80°C or higher to enable the eradication of viable bacteria, but if the temperature is too high, organic matter will be eluted from the ion exchange resin of the cartridge Polylasha. 1: The treated water boils, reducing operability and maintenance. Since the treatment system in the present invention is operated under normal pressure except for the filtration section, the heating temperature is most commonly kept below 100°C; If you adopt a method of heating at the same time, 10
It is also possible to heat to a high temperature exceeding 0°C, thereby making the effect of eradicating viable bacteria even more certain. However, if a practical heating temperature is considered, taking into account the heat resistance of the ion exchange resin, ultrafiltration membrane, piping, etc., about 110° C. is considered to be the upper limit. Considering the case where outside the high-temperature treatment system is used, pipes, pulp, tanks, etc. should be made or lined with polyvinylidene chloride resin, which has almost no eluted substances and has excellent heat resistance. The ultrafiltration membrane is also preferably made of a heat-resistant synthetic resin module.

In the illustrated example, raw water containing all kinds of impurities such as suspended solids, ions, viable bacteria, and organic matter is treated, and pretreatment,
Although the configuration shown is a combination of reverse osmosis, ion exchange, and ultrafiltration equipment, the arrangement order of each of these equipment can be changed as necessary, and the type of raw water (impurity It is also possible to omit some of the above devices depending on the type of device, etc.). Furthermore, the heating section for sterilization is not limited to the example shown in Figure 2, and it is also possible to perform heat sterilization treatment in other piping lines or storage tanks as long as it does not impede the purification ability unique to each treatment device. . However, in order to prevent back contamination of viable bacteria from the point of use and to remove viable bacteria more completely, the final line of purification treatment must be maintained in a high temperature sterilizing atmosphere as shown in Figure 2. It is better. It is also effective to provide an ultraviolet sterilizer in addition to the heat sterilizer to more completely eradicate viable bacteria.

The present invention is configured as described above, and viable bacteria can be almost completely removed by heating the treated water to 70 to 110°C at any location in the treatment system. Incidentally, Tables 1 and 2 below show the conventional method shown in Fig. 1 and the present invention method shown in Fig. 2 (heating temperature by heater = 80
This figure shows the water quality test results of each treated water (ultra-pure water) obtained at 30°C (°C).In particular, by employing the method of the present invention, there is no contamination of viable bacteria.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a conventional ultrapure water production method, and FIG. 2 is a flowchart showing an embodiment of the present invention. Applicant Kubota Iron Works Co., Ltd.

Claims (1)

[Claims] (1) In a method for producing pure water using unit operations such as reverse osmosis, ion exchange, ultrafiltration, microfiltration, and ultraviolet sterilization, either singly or in combination, the temperature of the treated water in part or the entire treatment system is set to 70°C.
A method for producing ultrapure water characterized by maintaining the temperature at ~110°C.