JPH0688025B2 - Ultrafiltration membrane device sterilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention uses an ultrafiltration membrane device to produce fine particles in water to be treated,
When removing colloidal substances, high molecular weight organic substances, exothermic substances, etc., by continuing the treatment, bacteria will propagate in the ultrafiltration membrane or the circulation pipe that supplies the permeated water of the ultrafiltration membrane device to the point of use. The present invention relates to a method for sterilizing an ultrafiltration membrane device when viable bacteria or fine particles leak into ultrapure water obtained from a point of use.

<Prior Art> Conventional ultrafiltration membrane devices equipped with various ultrafiltration membranes such as flat membranes, tubular membranes, spirals, and hollow fibers have been known to be fine particles in treated water, colloidal substances, high molecular organic matter, It is used to remove exothermic substances, etc., but in recent years it has been used to produce ultrapure water as cleaning water for semiconductor wafers or chips (hereinafter referred to as semiconductor wafers) in the electronics industry that produces LSI and VLSI. Often.

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

That is, the pure water 1 once stored in the pure water tank 2 is treated by the mixed bed polisher 3, the ultraviolet irradiation device 4, and the ultrafiltration membrane device 5, and the ions, fine particles, colloidal substances, and viable bacteria remaining in the primary pure water are treated. Etc. are removed as much as possible to obtain so-called ultrapure water. The ultrapure water which is the permeated water of the ultrafiltration membrane device 5 is supplied to the use point 7 surrounded by the one-dot chain line by the circulation pipe 6 and used as cleaning water here, and the remaining permeated water is supplied to the pure water tank 2. Circulate. The non-permeated water of the ultrafiltration membrane device 5 is also normally returned to the pure water tank 2 through the non-permeated water circulation pipe 8.

In the ultrafiltration membrane device 5 used for such an application, although the water to be treated is pure water obtained by the primary side pure water device, and is irradiated with ultraviolet rays immediately before. Use point 7 by long-time transparent processing
The quality of the ultrapure water obtained from the product deteriorates, and in particular the number of viable bacteria and fine particles increases.

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

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

The conventional sterilization treatment of the ultrafiltration membrane is 1 to 5
% Hydrogen peroxide solution, or a method of immersing in an oxidizing agent such as sodium hypochlorite solution, or washing by passing it through, the sterilization treatment using such an oxidizing agent is an ultrafiltration membrane or a component member of the apparatus. Is deteriorated, and a large amount of pure water is used for cleaning after sterilization. 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, as a sterilization treatment that does not deteriorate the ultrafiltration membrane and the components of the device and that can be washed relatively easily after the sterilization treatment,
A method of washing the ultrafiltration membrane with hot water is also used.

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

That is, the dotted line in FIG. 2 indicates the sterilization treatment line, and the treated water of the ultraviolet irradiation device 4 is stored in the storage tank 9 in advance, and when performing the sterilization treatment, the pure water in the storage tank 9 is heated. It is indirectly heated by using the 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 permeation treatment to obtain non-permeated hot water and permeated heat. The water is blown or circulated in the storage tank 9.

However, in the conventional sterilization with hot water, the hot water does not come into contact with the circulation pipe 6, so that there is a problem that even if general bacteria are propagated in a portion of the circulation pipe 6 where water is easily stagnant, this cannot be sterilized. Therefore, even if the treatment is restarted after the sterilization treatment of the ultrafiltration membrane device 5, there is a drawback in that the number of viable bacteria and the number of fine particles of the ultrapure water flowing out from the use point 7 does not decrease so much.

<Problems to be Solved by the Invention> The present invention is to solve the drawbacks of the conventional sterilization treatment when general bacteria propagate in the ultrafiltration membrane device 5 and the circulation pipe and the treatment performance thereof deteriorates. The present invention provides a sterilization method that does not deteriorate the ultrafiltration membrane or the constituent members of the device, can be easily washed after the sterilization treatment, and can also sterilize the circulation piping, and is low in cost and has an excellent treatment effect. The purpose is to

<Means for Solving Problems> In the present invention, the pure water obtained by the primary side pure water producing apparatus is once received in a pure water tank, and the pure water is treated with at least an ultraviolet irradiating apparatus, and then the ultrafiltration membrane apparatus is used. A method for producing ultrapure water that treats the treated water and circulates the treated water to the pure water tank by using a circulation pipe, and provides a use point in the system of the circulation pipe to supply a required amount of the treated water from the use point. In sterilizing the ultrafiltration membrane device in, heat the feed water of the ultrafiltration membrane device to hot water of 70 ℃ or more, supply the hot water to the ultrafiltration membrane device and permeate treatment Then, the heat permeable water is passed through the circulation pipe, passed through the point of use, and discharged at the downstream side of the point of use, which is a sterilization method for an ultrafiltration membrane device.

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

FIG. 1 is an explanatory diagram of a flow showing an example of an embodiment of the present invention, and a dotted line shows a sterilization treatment line as in FIG.

First, when the pure water in the pure water tank 2 is permeated, the pure water in the pure water tank 2 is treated by the mixed-bed polisher 3, the ultraviolet irradiation device 4, and the ultrafiltration membrane device 5 as in the conventional case, and the permeated water is then treated. Is circulated to the pure water tank 2 through the circulation pipe 6, and non-permeated water is also returned to the pure water tank 2 using the non-permeated water circulation pipe 8. 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, the water supplied to the ultrafiltration membrane device 5 is previously stored in the storage tank 9 during the permeation treatment.

In the sterilization process, the feed water in the storage tank 9 is used as a heat exchanger.
It is indirectly heated by 10 to obtain hot water having a temperature of about 90 ° C., and the hot water is supplied to the ultrafiltration membrane device 5 in the same direction as the permeation treatment. Then, the heat permeable water is lengthened to the circulation pipe 6,
After passing through the use point 7, the blow pipe 11 blows it out of the system. In some cases, youth point 7
The heat permeable water that has passed through can be collected in the storage tank 9, or can be fed to the pure water tank 2 and blown out of the system through the pure water tank.

A part of the hot water supplied to the ultrafiltration membrane device 5 is blown as non-permeated hot water.

The temperature of the hot water is preferably 70 ° C or higher, and usually around 90 ° C. 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 must be at least 15 minutes or more, and about 30 minutes is usually sufficient.

In the embodiment shown in FIG. 1, the feed water of the ultrafiltration membrane device was previously stored in the storage tank 9, and the stored feed water was used as hot water for sterilization treatment. The storage tank 9 can be omitted by heating with an exchanger to produce hot water.

<Effect> As described above, since the present invention allows hot water to pass through the ultrafiltration membrane, contaminants or general bacteria adhering to or growing on the membrane surface can be effectively stripped and sterilized by hot water. Further, the heat permeable water is passed through the circulation pipe 6, passes through the use point 7 and is discharged downstream of the use point 7, so that even if general bacteria propagate in the circulation pipe 6, this is effectively sterilized. Therefore, after the sterilization treatment, it is possible to obtain ultrapure water having a very small number of fine particles and viable bacteria from the use point 7. In addition, since the sterilization according to the present invention does not use an oxidizing agent, the constituent members of the apparatus are not deteriorated, and it is not particularly necessary to treat the cleaning waste liquid.

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.

After 500 hours from the above-mentioned normal operation, only the ultrafiltration membrane device was sterilized and washed by the conventional method with 2% hydrogen peroxide.

That is, an ultrafiltration membrane is added in the same direction as the direction in which hydrogen peroxide water is added to pure water in a storage tank in which pure water after the UV irradiation device is stored in advance to make it a hydrogen peroxide solution having a concentration of 2%. The device was supplied for 60 minutes for sterilization. Both the permeated liquid and the non-permeated liquid in the cleaning were circulated in the storage tank and reused.

In addition, only the ultrafiltration membrane device was sterilized and washed with hot water, which is a conventional method.

That is, in accordance with 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, and the pure water is heated to 90 ° C. by a heat exchanger to permeate the hot water. In the same direction as the direction, it was supplied to the ultrafiltration membrane device for 30 minutes and sterilized.

50% from the primary pure water, the permeated water at the beginning of operation at the point of use, the permeated water after 500 hours have passed, and the permeated water immediately after the above-mentioned conventional sterilization treatment and the sterilization treatment.
The number of fine particles of permeated water, the number of viable bacteria, and the specific resistance value after 0 hours were as shown in Table 1.

Next, the sterilization method of the present invention was carried out when 500 hours had elapsed from the sterilization treatment by the conventional method (hot water treatment).

That is, according to the flow of FIG. 1, the pure water after the ultraviolet irradiation device is taken out from a storage tank in which the pure water is stored in advance, and the pure water is heated to 90 ° C. by a heat exchanger to permeate the hot water. It is sterilized by supplying it to the ultrafiltration membrane device for 30 minutes in the same direction, and the non-permeated hot water obtained at this time is blown,
The heat-permeable water was passed through the circulation pipe to pass the point of use and then blown out of the system.

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 the table.

In addition, according to the present invention, the sterilization was performed using 2% hydrogen peroxide water, which is a conventional method, and the time required from the end of the sterilization until the specific resistance of the permeated water of the ultrafiltration membrane reaches 17 MΩ-cm. Sterilized and the permeated water has a resistivity of 17 MΩ immediately after the sterilization.
Table 2 shows the time required to reach -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 ... Ultrafiltration membrane device, 6 ... Circulation piping 7 ... Use point 8 ... Non-permeate water circulation Piping, 9 ... Storage tank 10 ... Heat exchanger, 11 ... Blow pipe

Claims (1)

[Claims] 1. Pure water obtained by the primary side pure water producing apparatus is once received in a pure water tank, treated with at least an ultraviolet irradiation apparatus, and then treated with an ultrafiltration membrane apparatus, and the treated water is circulated. The ultrafiltration membrane device in the method for producing ultrapure water, which circulates to the pure water tank using a pipe, provides a point of use in the system of the circulation pipe, and supplies a necessary amount of treated water from the point of use. In the sterilization treatment, the water supplied to the ultrafiltration membrane device is heated to 70 ° C. or higher, and the hot water is supplied to the ultrafiltration membrane device for permeation treatment,
A method for sterilizing an ultrafiltration membrane device, characterized in that the heat-permeable water is passed through the circulation pipe, passed through the point of use, and discharged on the downstream side of the point of use.