JPH0615022B2 - Ultrafiltration membrane device sterilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention uses a superfiltration membrane device to continue treatment when removing fine particles, colloidal substances, high molecular weight organic substances, exothermic substances, etc. in water to be treated. The present invention relates to a method for bacteria in an ultrafiltration membrane device when bacteria propagate in the permeation pipe or the like after the ultrafiltration membrane or the ultrafiltration membrane device and live bacteria or fine particles leak into the permeate.

<Prior art> Conventional ultrafiltration membrane devices equipped with various types of ultrafiltration membranes such as flat membrane, tubular membrane, spiral, and hollow fiber are known to be fine particles in treated water, colloidal substances, high molecular organic substances, and exothermicity. It is used to remove substances, but in recent years L
It is often used for producing ultrapure water as water for cleaning semiconductor wafers or chips (hereinafter referred to as semiconductor wafers) in the electronic industry that produces SI and VLSI.

Water for cleaning such semiconductor wafers is usually produced by the following flow. That is, the raw water is treated with a primary side water supply device such as a coagulating sedimentation device, a sand filter, an activated carbon filter device, a reverse osmosis membrane device, a 2-bed 3-tower pure water production device, a mixed bed polisher, and a precision filter to obtain pure water. Immediately before obtaining and then cleaning the semiconductor wafer, the primary treated pure water is treated by the secondary side water supply device as shown in FIG.

That is, the pure water 1 is temporarily stored in the pure water tank 2, and the pure water is treated by the mixed-bed polisher 3, the ultraviolet irradiation device 4, and the ultrafiltration membrane device 5, and the ions and fine particles remaining in the primary treated pure water, The so-called ultrapure water is obtained by removing colloidal substances and viable bacteria as much as possible. The ultrapure water, which is the permeated water of the ultrafiltration membrane device 5, is transferred to the use point 7 surrounded by the alternate long and short dash line through the use point pipe 6 and used as cleaning water here. The remaining permeated water is transferred to the pure water tank 2. Circulate. The non-permeated water of the ultrafiltration membrane device 5 is also usually returned to the pure water tank 2 through the non-permeated water circulation pipe 8.

The ultrafiltration membrane device 5 used for such an application has a long life despite the fact that the water to be treated is pure water obtained by the primary side water supply device and is irradiated with ultraviolet rays immediately before. The permeation treatment for a period of time increases the amount of viable bacteria and fine particles leaking into the permeate.

It is considered that this is because general sterilization having resistance to ultraviolet rays propagates in pure water, which is the water to be treated of the ultrafiltration membrane device 5, on the membrane surface or the like.

Therefore, if the ultrafiltration membrane to be used is contaminated as described above, it is necessary to perform some sterilization treatment.

The sterilization treatment of ultrafiltration membranes that has been performed conventionally is 1-5%
There is a method of immersing in the hydrogen peroxide solution or the oxidizing agent such as sodium hypochlorite solution, or washing by passing it through, but the sterilization using such an oxidation example deteriorates the ultrafiltration membrane or the components of the device. There is also a drawback in that a large amount of pure water is used for cleaning after the sterilization treatment. Furthermore, since a relatively large amount of oxidant is used, there is a problem that the chemical cost and the waste liquid treatment cost are high.

On the other hand, a method of washing the ultrafiltration membrane with hot water is also used as a sterilization treatment that does not deteriorate the ultrafiltration membrane and the components of the apparatus and can be washed relatively easily after the sterilization treatment.

The conventional sterilization treatment with hot water is performed as follows.

That is, a thousand indicated by a dotted line in FIG. 2 indicates a sterilization treatment line, and the treated water of the ultraviolet irradiation device 4 is stored in the storage tank 9 in advance, and the sterilization treatment is performed in the storage tank 9 in advance. Pure water is indirectly heated using the heat exchanger 10 to form hot water of about 90 ° C., and the hot water is passed through the ultrafiltration membrane device 5 in the same direction as the filtration treatment to obtain non-permeation heat. Water and permeated hot water are blown or circulated in the pure water tank 2.

However, such conventional sterilization has a drawback that the sterilizing effect is small. Further, since hot water does not come into contact with the use point arrangement 6, there is also a problem in that even if general bacteria propagate in a portion of the use point pipe where water tends to stay, it cannot be sterilized.

<Problems to be Solved by the Invention> The present invention is to solve the drawbacks of the conventional sterilization treatment when general sterilization propagates in the ultrafiltration membrane device 5 or its surrounding pipes and the treatment performance thereof deteriorates. It provides a sterilization method that does not deteriorate the ultrafiltration membrane or the components of the device, can be easily cleaned after sterilization treatment, and can also sterilize the point-of-use piping, and is low cost and has excellent treatment effects. The purpose is to do.

<Means for Solving Problems> Washing with hot water in the conventional sterilization method described above utilizes the sterilizing property of hot water, but if the sterilizing effect is excellent, It is an excellent method as a sterilization method for an ultrafiltration membrane for producing water for cleaning semiconductor wafers, since it has advantages such as ease of cleaning after sterilization treatment and no deterioration of the ultrafiltration membrane.

The present inventor has variously studied the performance improvement of the sterilization treatment in the conventional hot water washing, and supplies hot water to the ultrafiltration membrane through the point of use piping and reverses the case of filtering the hot water. After washing through the ultrafiltration membrane in the direction,
It was found that the performance after the sterilization treatment is significantly improved.

The present invention is based on the above knowledge, and in sterilizing the ultrafiltration membrane device which again performs the filtration treatment of the pure water obtained in the primary side pure water production device, immediately before the point of use, the permeated water of the ultrafiltration membrane device. Is heated to form hot water of 70 ° C. or higher, the hot water is supplied to the ultrafiltration membrane through the point of use piping, and the hot water is filtered in the opposite direction to the method of filtering. It is a method for sterilizing an ultrafiltration membrane, which is characterized in that

<Operation> The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory view of a flow showing an example of an embodiment of the present invention, the dotted line shows a sterilization treatment line, and 11 to 21 show typical valves as in FIG.

First, when the pure water in the pure water tank 2 is filtered, the valves 18, 15, 15, 12 and 16 are opened and the other valves are closed as in the conventional case, and the pure water in the pure water tank 2 is mixed-bed polisher. 3, the ultraviolet irradiation device 4 and the ultrafiltration membrane device 5, the permeated water is circulated to the pure water tank 2 through the use point pipe 6, and the non-permeated water is also clarified by the non-permeated water circulation pipe 8.
Return to. Ultrapure water required at the use point 7 is sampled and used as cleaning water for semiconductor wafers and the like.

Next, the sterilization treatment with hot water in the present invention is performed as follows.

That is, during the filtration process, the valve 11 is opened and the storage tank 9 is opened.
Store permeate in advance.

In the sterilization process, valve 13, valve 15, valve 17, valve 1
9, the valve 20 is opened, the other valves are closed, and the permeated water in the storage tank 9 is indirectly heated by the heat exchanger 10 into hot water having a temperature of about 90 ° C., and the hot water is used as a use point pipe. 6 and then passes through the point of use 7 and is supplied to the ultrafiltration membrane device 5 in the direction opposite to the filtration process.

The hot water supplied to the ultrafiltration membrane device 5 and a part thereof are blown from the valve 20 as non-permeated hot water, and the other portion is passed through the ultrafiltration membrane in the direction opposite to the filtration process, and the permeated hot water is passed through the valve 17. Through the valve 19 to blow.

In some cases, the valve 11 may be opened to circulate a part or all of the permeated hot water to the storage tank 9. The temperature of hot water is preferably 70 ° C or higher, usually 90 ° C.
Before and after. It should be noted that a temperature of 70 ° C. or lower is not preferable because the regenerative effect becomes small.

Next, the cleaning time needs to be at least 15 minutes or more, and about 30 is usually sufficient.

As described above, the present invention is to pass the hot water through the ultrafiltration membrane in the direction opposite to the direction in which the hot water is filtered. It doesn't matter.

That is, the valve 13, the valve 14, the valve 17, the valve 19, and the valve 20 are opened, the other valves are closed, and hot water is used for the use point piping 6
Flow into the ultrafiltration membrane device 5 through the point of use 7
In the same direction as the filtration process.

A part of the hot water supplied to the ultrafiltration membrane device 5 is blown from the valve 19 via the valve 17 as non-permeated hot water, and the permeated hot water is blown via the valve 20. In some cases, the valve 21 may be opened to circulate a part or all of the permeated hot water to the storage tank 9.

In the embodiment shown in FIG. 1, the permeated water was stored in the storage tank 9 in advance, and the stored permeated water was used as hot water for the sterilization treatment. For example, the permeated water is obtained by one ultrafiltration membrane device 5, and the permeated water is used as hot water, whereby the storage tank 9 can be omitted.

<Effect> As described above, according to the present invention, the hot water is passed through the ultrafiltration membrane in the direction opposite to the filtration direction, so that the contaminants or general bacteria adhering to or propagating on the membrane surface flow back from the backside of the membrane. It can be effectively peeled off and sterilized by hot water, and its bactericidal effect is remarkably excellent as compared with the conventional sterilization treatment in which hot water is passed through the membrane surface in the same direction as the filtering direction. There is.

Further, since hot water is supplied to the ultrafiltration membrane device 5 through the use point pipe 6 through the use point 7, it is possible to effectively sterilize general bacteria even if the use point pipe 6 is propagated. After the sterilization treatment, it is possible to obtain permeated water having a very small number of fine particles and a very small number of viable bacteria.

Examples will be described below in order to clarify the effects of the present invention.

Example Raw water turbidized by a turbidity filtration device was treated by a reverse osmosis membrane device, then treated by a two-bed, three-column type pure water production device, and the treated water was deaerated by a vacuum deaeration tower, and then a mixed-bed type Pure water filtered by a microfilter (0.45 μm) was stored in a pure water tank.

This pure water was treated with a mixed bed polisher and an ultraviolet irradiation device, and then fed to an ultrafiltration membrane device equipped with a polysulfone-based hollow fiber ultrafiltration membrane.

The conventional hot water sterilization was performed after 500 hours from the above normal operation.

That is, according to the flow of FIG. 2, the pure water after the ultraviolet irradiation device is taken out from the storage tank in which the pure water is stored in advance, the pure water is heated to 90 ° C. by a heat exchanger, and the hot water is filtered. In the same direction as the direction, it was supplied to the ultrafiltration membrane device for 30 minutes and sterilized.

Permeate at the beginning of operation at the primary pure water and at the point of use, permeate after 500 hours has passed, permeate immediately after sterilization by the conventional method and permeated water at 500 hours after the sterilization, the number of viable bacteria, The first specific resistance value
It was as shown in the table.

Next, the sterilization method of the present invention was carried out when 500 hours had passed since the sterilization treatment by the conventional method.

That is, in accordance with the flow of FIG. 1, the permeated water of the ultrafiltration membrane device is taken out from the storage tank in which the permeated water is stored in advance, and the permeated water is heated to 90 ° C. by a heat exchanger, and the hot water is used as a use point. Through the use point piping,
It was sterilized by supplying it to the ultrafiltration membrane device for 30 minutes in the direction opposite to the filtration direction.

Immediately after the sterilization treatment by the method of the present invention and 500 hours after the sterilization treatment, the number of fine particles, the number of viable bacteria and the specific resistance value are shown in Table 1.

The conventional method was sterilization using 2% hydrogen peroxide solution, and the time required from the completion of the sterilization until the specific resistance of the permeate of the ultrafiltration membrane reached 17 MΩ-cm and the sterilization by the present invention. However, immediately after the end, the permeated water has a resistivity of 17M.
Table 2 shows the time required to reach Ω-cm.

As shown in the above examples, the sterilization method according to the present invention can obtain permeated water in both the fine particle number and the viable cell count as compared with the sterilization method according to the conventional method, and compared with the sterilization method using hydrogen peroxide solution. Then, the cleaning after the sterilization treatment is short, and the amount of pure water consumed for the cleaning is extremely small.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a flow of an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a conventional flow. 1 ... Pure water, 2 ... Pure water tank 3 ... Mixed bed polisher, 4 ... Ultraviolet irradiation device 5 ... Ultra filtration membrane device 6 ... Use point piping, 7 ... Use point 8 ... Specific permeate water circulation Piping, 9 ... Storage tank 10 ... Heat exchanger, 11-21 ... Valve

Claims (1)

[Claims] 1. When sterilizing the ultrafiltration membrane device in which pure water obtained by the primary side pure water production device is filtered again immediately before the point of use, the permeated water of the ultrafiltration membrane device is heated to 70 Characterized in that it is not hot water above ℃, the hot water is supplied to the ultrafiltration membrane through the point of use piping, and the hot water is passed through the ultrafiltration membrane in the opposite direction to the method of filtering. Method for sterilizing ultrafiltration membrane device.