JPH0994585A - Method for producing ultrapure water and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce highly purified ultrapure water reduced in the concn. of org. matter inclusive of urea by adding hypochlorite or alkali bromide and zincate to water to be treated under a specific pH value condition to decompose urea in the water to be treated. SOLUTION: Raw water is introduced into a pH adjusting tank 101 to be adjusted to 4-8 in pH by the injection of chemicals from a hydrochloric acid storage tank 102 and a caustic soda storage tank 103 and sent to a flocculation filter 105 and, on the way of a water sending pipe 106, a flocculant is injected into the raw water from a flocculant storage tank 104 and, if necessary, sodium bromide being one of urea decomposing agents is injected in and added to raw water from a sodium bromide soln. storage tank 130 by an injection pump 131. By this constitution, suspended fine particles in raw water become flocs and the raw water is subjected to solid-liquid separation by the flocculation filter 105 to be sent to a reaction tank 107 and, on the way of a water sending pipe 108, sodium hypochlorlte being other agent as a urea decomposing agent is injected and added if necessary from a sodium hypochlorite storage tank 140 by an injection pump 141 to decompose urea.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing high-purity water generally called ultrapure water, and more particularly to an apparatus and an apparatus for producing ultrapure water capable of removing urea.

[0002]

2. Description of the Related Art Ultrapure water (hereinafter, high-purity water generally referred to as pure water, ultrapure water, and ultrapure water is generally referred to as "ultrapure water") is used in the semiconductor industry, nuclear industry, pharmaceutical industry, Pharmaceutical manufacturing,
It is used as water in various fields such as microbial engineering and chemical analysis, and the required water quality is not uniform in each field, but fine particles, ions, organic substances, bacteria contained in it as city water, groundwater, industrial water, etc. It is manufactured by performing a multi-step purification process for removing gases and the like (hereinafter referred to as "impurities and the like"). Of these, in ultrapure water represented by water for manufacturing semiconductors, integrated circuits, and water for manufacturing pharmaceuticals, removal of contained organic substances is one of the most important things. Regarding the water quality evaluation of ultrapure water related to organic substances, it is difficult to quantify the organic substances in the ultrapure water that has undergone the above-described multi-step purification treatment, because the amount is very small. Therefore, in general, T using carbon that constitutes an organic substance as an index
It is performed by quantitative measurement of OC (total organic carbon).

As a purification treatment process for removing organic substances, which is generally adopted in conventional ultrapure water production equipment, ion exchange equipment and the like can be removed to a certain extent, but as a main process, a reverse osmosis membrane and There are membrane treatments such as outer filtration membranes, decomposition treatment by ultraviolet rays combined with an oxidizing agent, and decomposition treatments by ultraviolet rays not combined with an oxidizing agent.

By the way, even in the conventional ultrapure water production facility having such a purification treatment process for removing organic substances, the TOC concentration of the produced ultrapure water changes with time and a special example. It is known that there is a limit to the reduction of TOC concentration, and this problem is caused by urea, which is an organic substance that is difficult to decompose and is contained in raw water, as described in JP-A-6-86997. It has been known.
That is, low molecular weight and chemically stable urea ((NH ₂ )
₂ CO) is difficult to remove by membrane treatment,
In the decomposition and removal method using ultraviolet rays, it is difficult to obtain a large-capacity low-pressure mercury lamp capable of irradiating short-wavelength ultraviolet rays (mainly 254 nm), which has a larger energy than high-pressure mercury lamps, and therefore decomposition is not easy, resulting in ultrapure water. This is because it is difficult to prevent leakage into the inside. In most cases, urea is contained in the raw water in a short-term, rather than in a constant manner.

However, in the recent various industrial fields in which more highly purified water is required, ultrapure water has always been contained in a very small amount and constantly. However, the removal of urea, which is a large part of the TOC concentration at that time, although it is mostly contained temporarily for a short period of time, requires the shutdown of industrial equipment using this as water. There is a growing need to prevent it.

Conventionally, as means for removing such urea, according to the above-mentioned JP-A-6-86997, an ultrapure water producing apparatus equipped with a pretreatment apparatus, a primary pure water producing apparatus, and a secondary pure water producing apparatus is used. It has been proposed to install an enzyme decomposing device in which urease, which is a urea degrading enzyme, is supported on an appropriate carrier in the pretreatment device.

[0007]

However, in the conventional method using the above enzyme, it is not easy to maintain the activity of the enzyme over a long continuous operation period, and most ultrapure water production facilities Then, it is sufficient to deal with the temporary and short-term increase in raw water urea concentration for a very short period of time. However, the above-mentioned method has a facility disadvantage that the enzyme decomposition apparatus must be permanently installed for this purpose. is there. Furthermore, although depending on the structure of the enzyme carrier and the like, there is a problem in that the backwash must be performed at regular intervals in consideration of the clogging of SS, which complicates operation management.

In view of the recent situation in which the highly purified water in which the concentration of organic substances including urea is further reduced has been demanded in the above various industrial fields as described above, Further, various studies have been repeated to provide a novel urea removal method that can solve the problems of the conventional techniques using the above biochemical methods.

In an ultrapure water production facility equipped with a multi-stage treatment device for removing impurities and the like, adding an ionic substance, which is one of the important removal targets, from outside the system causes a salt load. Although this has not been considered in the past because it will result in an unreasonable increase in the amount of urea, if the hypohalite ion is used under the control that satisfies predetermined conditions for the decomposition and removal of trace amounts of urea, it will decompose and remove urea. The present inventor has found that a constitution suitable for producing pure high-purity water can be adopted, and further, according to this method, the drawbacks of the conventional method using the enzyme described above can be solved to form the present invention. Came to.

One of the objects of the present invention made from this point of view is to provide a method and an apparatus capable of producing highly purified ultrapure water containing urea and having a further reduced organic matter concentration. .

Another object of the present invention is to replace the conventional technique using a biochemical method with a chemical method and easily deal with a temporary short-term increase in the raw water urea concentration,
Another object of the present invention is to provide a method and apparatus for producing ultrapure water, which is capable of removing urea simply by installing auxiliary equipment that is simple in structure and operation such as chemical addition means.

Still another object of the present invention is that the enzyme carrier in the prior art and a water passage device therefor are not required, and backwashing treatment for clogging is not necessary, and the operation and management of the equipment are easy. Another object of the present invention is to provide a method and an apparatus for producing ultrapure water having a urea removing ability.

Another object of the present invention is to enable the urea removal treatment to be carried out quickly when the urea concentration of the raw water rises, so that the ultrapure water produced by performing the multi-stage purification treatment can be used in many cases. First of all, it is possible to reliably prevent urea from leaking,
An object of the present invention is to provide a monitoring system that is effective in constructing an ultrapure water production system that can prevent the operation stop of industrial equipment that uses ultrapure water as water, and an equipment operating method using this monitoring system. Monitoring of such an increase in the urea concentration of raw water is not necessary in the conventional method in which the urea decomposing enzyme is permanently installed in the water passage, but the urea decomposing treatment is carried out by temporarily adding a chemical as in the present invention. It is extremely important for the method, and the significance of the provision of the monitoring system of the present invention is extremely large in the present situation where no effective urea monitor is known.

[0014]

The above-mentioned various objects can be achieved by the invention described in each of the claims.

One of the features of the invention provided by the present application is that
A method for producing ultrapure water by performing a multi-step purification process for removing fine particles, ions, organic substances, bacteria, and gas in water to be treated, wherein hypobromite is used under the condition of water to be treated pH 4 to 8. Is added to decompose urea in the water to be treated, which is a method for producing ultrapure water.

Performing the above treatment under the condition that the water to be treated has a pH of 4 to 8 is an essential condition for removing a very small amount of urea contained in special high-purity water called ultrapure water.
That is, when the pH is less than 4, it is difficult to industrially implement it because the hypobromite ion is gasified due to the addition of the above-mentioned agent. On the other hand, when the pH is more than 8, the oxidizing power of the hypobromite ion is high. It is difficult to put it into practice because it decreases and the reaction stagnates. For these reasons, the pH of the water to be treated is more preferably 5.5 to 7.5, most preferably pH 6.0 to 6.0.
It is preferably 6.5. In order to satisfy this pH condition, an operation of adding a pH adjusting substance to the raw water from outside the system may be performed. However, since it is a reaction in equipment for producing ultrapure water, at a position where the pH condition is satisfied during general ultrapure water treatment, in order not to increase the salt load of the ion removing device more than necessary. It is more preferable to perform the above-mentioned urea decomposition treatment because the salt load is not increased.

The above-mentioned hypobromite added for the decomposition of urea is not limited, but sodium hypobromite is typically used. The addition amount of this hypobromite to be added to the water to be treated is 3 to 90, preferably 3 to 15 molar ratio to urea in the water to be treated. The reaction in the case of reacting urea and hypobromite ions by adding hypobromite to the water to be treated is shown by the following formula.

(NH ₂ ) ₂ CO + 3BrO ⁻ → N ₂ + CO ₂ + 2H ₂ O + 3Br .. (1) As can be seen from this reaction formula (1), the hypochlorous acid necessary for decomposing urea contained in the water to be treated is shown. The theoretical value of bromate is 3 but the molar ratio is preferably 3 or more in order to perform the decomposition treatment of the contained urea which is expected in actual industrial practice as quickly as possible. That is, if the molar ratio of hypobromite ion to urea is increased, the reaction chance of the above formula (1) increases and the processing time is shortened. However, when the amount of hypobromite added exceeds the expected amount of urea in a molar ratio of 15 or more, the increasing tendency of the treatment rate becomes small, and the salt load becomes unnecessarily large in the process of ultrapure water production. Doing so will increase the load on the ion exchange apparatus and the like, so it is not preferable that the molar ratio exceeds 90 at the maximum. Therefore, the amount of hypobromite added is in the above range.

In the present invention, instead of the above hypobromite, hypochlorite and alkali bromide can be used under the condition of pH 4-8. In this case, potassium bromide and sodium bromide are typically used as the alkali bromide, and sodium hypochlorite is typically used as the hypochlorite. The addition amount of hypochlorite to be added to the water to be treated is 10 to a molar ratio with respect to urea in the water to be treated.
It is 2000, preferably 30 to 600. Molar ratio 10
If less than, there is a problem that the rate of decomposition of urea is slow,
On the other hand, when the molar ratio exceeds 600, the decomposition time becomes sufficiently short, but the salt load tends to increase, so that it is not preferable that the molar ratio exceeds 2000 even at the maximum. The theoretical amount of alkali bromide added is, as shown by the following formula, a molar ratio of 3 to urea in the water to be treated. That is, the reaction when water to be treated for producing ultrapure water is reacted with sodium hypochlorite as sodium hypochlorite and sodium bromide as alkali bromide is shown as follows: Br ⁻ + ClO → BrO ⁻ + Cl ⁻・ (2) (NH ₂ ) ₂ CO + 3BrO ⁻ → N ₂ + CO ₂ + 2H ₂ O + 3Br ⁻・ (3) The substance balance according to the reaction formulas (2) and (3) is represented by the following formula (4) ).

(NH ₂ ) ₂ CO + 3NaBr + 3NaClO → N ₂ + CO ₂ + 2H ₂ O + 6Na ⁺ + 3Br ⁻ + 3Cl ^−. Since this is a by-product and further reacts with hypochlorous acid, when the bromide ion has a flow that can be effectively utilized for the repeated reaction, the amount of sodium bromide to be actually added is determined by the above formula (4). In some cases, it is not necessary that the molar ratio be 3). When the urea concentration in the water to be treated is as low as 100 to 500 ppb, the above reaction does not proceed theoretically because it is dilute, and therefore the amount of alkali bromide added should be increased, for example, in the water to be treated. It is often preferred to have a molar ratio of 30 to 60 with respect to urea.

In the method of producing ultrapure water by performing a multi-step purification treatment for removing impurities and the like in the water to be treated as described in claim 8, instead of the above method, the pH of the water to be treated is It is also possible to produce ultrapure water by adding alkali bromide and ozone under the conditions of pH 4 to 10, preferably pH 6 to 8, to decompose urea in the water to be treated.

If the pH of the water to be treated is less than 4, the hypobromite ion may be gasified. On the contrary, pH
Ozone shows a high oxidizing power even if it exceeds 10, but it is not preferable to adjust the pH of the water to be treated to exceed 10 because it results in an increased salt load, and therefore is in the above range. In order to satisfy the above pH conditions, the pH adjusting substance may be added to the raw water from outside the system,
It is preferable to perform the above-mentioned urea decomposition treatment at a position where the pH condition is accompanied by the conventional ordinary ultrapure water treatment so that the salt load of the ion removing device provided in the facility is not increased more than necessary.

The method using alkali bromide and ozone as the urea decomposer increases the salt load in the water to be treated, as compared with the method using hypobromite, or alkali bromide and hypochlorite. It is more preferable to use as a method for decomposing urea contained in ultrapure water because it is advantageous in that it does not cause it and that exhaust gas ozone released in the gas phase without contributing to the reaction can be recovered and recycled. To be done. In this method, as the alkali bromide, potassium bromide or sodium bromide can be used as in the above case. As in the case described above, when the amount of alkali bromide added is such that the bromide ion can be effectively utilized for the repeated reaction,
The actual amount of sodium bromide to be added may be less than the molar ratio of 3, but the urea concentration in the treated water is 100 to 50.
When the concentration is as low as 0 ppb, the above reaction may not proceed theoretically due to the dilution, and therefore the amount of alkali bromide added should be, for example, a molar ratio of 30 to 60 with respect to urea in the water to be treated. It is often preferable to increase the number.

The addition amount of ozone is 3 to 10, preferably 3 to 6, in molar ratio with respect to urea in the water to be treated. If the molar ratio is less than 3, the oxidation of bromide ion to hypobromite ion does not proceed sufficiently. On the contrary, if the molar ratio exceeds 10, excess ozone produces bromate ion that does not contribute to the urea decomposition reaction as a by-product. Therefore, it is not preferable, and thus the above range is set.

The present application also provides an apparatus for producing ultrapure water for carrying out any one of the above-mentioned methods, and one of the characteristics of the apparatus is the fine particles, ions,
A urea decomposition treatment means is provided at any position of the ultrapure water producing apparatus equipped with multi-stage treatment means for removing organic substances, bacteria, and gas, and the urea decomposition treatment means is used to remove urea in the water to be treated. A means for adding a urea decomposing agent that decomposes, and a tank-type and piping-type reaction water passage set so as to maintain a sufficient water passage time for decomposition of all urea in the water to be treated following the addition position of the addition means. The ion removing means is provided at the latter stage of this reaction water passage. The ion removing means may be used as a common ion exchange device or the like installed in a normal ultrapure water producing device, or may be separately provided separately.

Among the above-mentioned urea decomposition treatment means, means for adding a urea decomposition agent is as follows (1) to
It is provided as a means for adding any one of the decomposing agents listed in (3).

(1) hypobromite, (2) alkali bromide and sodium hypochlorite, (3) alkali bromide and ozone, and in the cases of (2) and (3), two agents The addition positions may be the same or different, and may be mixed before addition, and the addition method is not limited in any of the above cases.

The ultrapure water production system of the present invention having the above-mentioned structure is not limited, but it is conventionally composed of a combination of a general pretreatment system, a primary pure water production system and a secondary pure water production system. A configuration similar to a general one can be adopted. For example, as each treatment means provided in multiple stages to remove impurities and the like in the water to be treated to produce ultrapure water, a coagulation provided as so-called pretreatment equipment for removing suspended substances and fine particles Examples include precipitation / filtration devices and microfloc filters. Similarly, ion removal devices, reverse osmosis membrane devices for removing ions, reverse osmosis membrane devices, precision filters, ultrafiltration membranes for removing organic substances. Equipment, decarbonation tower, ultraviolet oxidation equipment, reverse osmosis membrane equipment for removing microorganisms such as bacteria, ultraviolet sterilization equipment, vacuum degassing tower, decarbonation tower, membrane degassing equipment for gas removal Each of them can be exemplified as a representative example, and appropriate means are selected from these depending on the type and amount of impurities contained in raw water, and the water quality requirement of ultrapure water to be produced. Pure water production equipment is formed That.

As described above, the characteristic feature of the ultrapure water producing apparatus is that, in the apparatus having the above-mentioned multistage treatment means, firstly, the decomposition treatment of urea contained in the water to be treated is performed. Secondly, a means for adding the urea decomposing agent is provided. Secondly, a reaction passage for ensuring a sufficient passage time for decomposing all urea in the water to be treated is provided downstream of the position where the urea decomposing agent is added. Removal of ions such as bromine ions and sodium ions remaining after decomposing urea in the water channel and water channel for this reaction, and further ion exchange device for removing CO ₂ generated by urea decomposition, reverse osmosis membrane, etc. Since the means is provided, the water passage among them can be provided as a tank or a pipe (water passage) for retaining and holding the water to be treated. Further, although it can be specially provided for the decomposition of urea, it is also preferable to use a part of a conventional device such as a tank or a pipe as a water passage for reaction which performs the above-mentioned action. Specifically, it is often preferable to provide the urea decomposition treatment means at any position upstream of the secondary pure water producing apparatus, and particularly, the treated water retention tank and pH provided in the pretreatment apparatus. When an adjusting tank or the like is used as the above-mentioned water passage for reaction, the water to be treated is usually retained in this retention tank for about 1 to 3 hours, so that it is not particularly necessary to provide a special tank or pipe, which is particularly preferable.

In the apparatus of the present invention in which the urea decomposing agent is added, the above-mentioned water passage for reaction and an ion exchange resin or a reverse osmosis membrane for removing the ions remaining after decomposing urea are provided. It is preferable to adopt a configuration in which an activated carbon tank for decomposing and removing an oxidative urea decomposing agent such as hypohalite ion or ozone is provided in between, thereby preventing oxidative deterioration of the ion exchange resin and the reverse osmosis membrane. To be done.

In the ultrapure water production system of the present invention,
A configuration is preferably adopted in which a urea monitoring device for continuously detecting the urea concentration in the water to be treated is provided at an upstream position of the urea decomposition treatment means, that is, in the middle of the water passage from the raw water intake to the urea decomposition treatment means. .

The water passage length from the urea decomposition means to the urea monitoring device is longer than the time required for the urea monitoring device to detect the urea concentration, and is longer than the time required for the treated water to pass through this water passage. It is particularly preferable to set so as to be sufficiently long. With this configuration, the urea decomposing means is normally stopped, and when the urea monitoring device detects that the urea concentration in the water to be treated used for ultrapure water production has temporarily increased. By operating the urea decomposition means, it is possible to maintain the water quality of continuously produced ultrapure water in a highly pure state with a low TOC concentration, regardless of fluctuations in the urea concentration in the water to be treated.

Further, in the ultrapure water producing system provided with the above urea monitoring device, the means for detecting an increase in the urea concentration by the urea monitoring device and outputting a signal, and the operation of the urea decomposition processing means upon receiving the signal. By providing a drive control means for starting the operation, it is possible to perform automated operation management of the apparatus.

The urea monitoring apparatus used in the above ultrapure water producing apparatus includes a branch pipe that branches from a water passage to continuously take in the water to be treated, and an ion remover for removing ions contained in the water to be treated. It is possible to exemplify a device provided with a means and a TOC measuring means for measuring the total organic carbon (TOC) contained in the water to be treated after ion removal. Since other organic substances are removed, only urea can be detected, and when raw water containing urea is taken, it can be detected with a time delay of about 10 minutes.

According to the above-described method and apparatus for producing ultrapure water of the present invention, the decomposition agent of the decomposing agent can be used in the region where the concentration of urea contained in the water to be treated used for producing ultrapure water is 10 mg / liter or less. Although it depends on the conditions such as concentration and treatment pH, even under the special condition that it is not preferable to increase the salt load of the water to be treated, that is, the production of ultrapure water, decomposition of urea of 90% or more within 3 hours of reaction time That is, an excellent effect is obtained.

[0036]

【Example】

Example 1 FIG. 1 is a flow chart showing a schematic configuration of Example 1 of an ultrapure water production system to which the present invention is applied, in which 1 is a pretreatment unit, 2 is a primary pure water treatment unit, The primary pure water produced by this primary pure water treatment device is sent to the subsystem 3, which is a secondary pure water treatment device.

The present embodiment is characterized in that the pretreatment device 1 has a urea decomposition treatment device incorporated therein.

Explaining the structure of the pretreatment apparatus 1, raw water (water to be treated) is first introduced into the pH adjusting tank 101, and the pH is adjusted by chemical injection from the hydrochloric acid storage tank 102 and the caustic soda storage tank 103. The pH-adjusted water to be treated is fed to the coagulation filter 105, and a coagulant such as aluminum sulfate or polyaluminum chloride (PAC) is injected from the coagulant storage tank 104 in the middle of the water supply pipe 106. However, when necessary, sodium bromide, which is one of the urea decomposition agents, is injected and added from the sodium bromide solution storage tank 130 by the injection pump 131. The injection addition control of this sodium bromide will be described later.

By injecting the above coagulant, suspended fine particles in the water to be treated become coagulated flocs, and the above coagulated filter 1
The water to be treated is subjected to solid-liquid separation in 05, and the separated water to be treated is sent from the coagulation filter 105 to the reaction tank 107.
In the middle of step 8, sodium hypochlorite, which is another agent of the urea decomposing agent, is injected from the sodium hypochlorite solution storage tank 140 by the injection pump 141 when necessary. In the apparatus of this example, as described above, sodium bromide, which is one agent of the urea decomposing agent, is added on the upstream side of the coagulation filter 105, and sodium hypochlorite, which is another agent of the urea decomposing agent, is coagulated and filtered. Although it was configured to be added downstream of the vessel 105,
The position of addition of both decomposing agents and the order of addition are not limited to this. For example, both decomposing agents may be added almost simultaneously at the downstream side of the coagulation filter 105. The reaction tank 107 has a water passage for reaction for decomposition of urea in a tank form, and is provided with a capacity capable of ensuring a predetermined residence time necessary for decomposition of urea contained in the water to be treated.
The water to be treated that has undergone the urea decomposition treatment is then activated carbon tower 109.
The residual sodium hypochlorite is decomposed and removed by passing through the pretreatment, and the pretreatment is completed.

The water to be treated which has been treated by the above pretreatment apparatus 1 is then sent to the primary pure water producing apparatus 2, and in this example, first, for example, a two-bed, three-column type ion exchange apparatus 201 filled with an ion exchange resin, Ion removal in the reverse osmosis membrane device 202,
After the organic substances are removed, the water is stored in the primary pure water tank 203 and is sent to the subsystem 3. In this example, for the sake of simplicity of explanation, the primary pure water producing apparatus 2 is illustrated by illustrating only two of the above-mentioned ion exchange apparatus 201 and reverse osmosis membrane apparatus 202, but this is not the only case. It goes without saying that a decarbonation tower or a vacuum deaeration tower for the above, or an ultraviolet irradiation device for sterilization or the like may be installed. Although not shown, the subsystem is used to perform a process for producing higher-purity ultrapure water using a known processing apparatus.

In the ultrapure water production system of the present embodiment having the above-mentioned structure, the treatment when the raw water contains urea will be described.

In this example, a branch pipe 122 is provided for branching a part of the raw water flowing into the pH adjusting tank 101 and constantly flowing it to the urea monitoring device 120. Water is taken from the branch pipe 122. Raw water is supplied to the urea monitoring device 120.
The urea concentration is continuously measured and monitored by. As shown in FIG. 2, the urea monitoring device 120 in this example is a mixed bed type ion exchange resin tower type ion removing device (ion removing device) for removing ions in raw water (water to be treated) and organic substances other than urea. After that, the raw water is passed through 1201 and the TOC measuring device 1202 using the existing carbon as an index is passed through the raw water. With this configuration, the measured value of the electric conductivity meter installed before and after the ultraviolet irradiation device (high pressure type) is largely changed by the high electric conductivity of CO ₂ or NO ₃ generated by the decomposition of urea, so that urea is converted into raw water. Is detected.

The measurement information measured by the urea monitoring device 120 is sent to the control device 121 composed of a microcomputer (MPU) and the like, and when urea is detected in the raw water, the injection pump 131 is operated. A command signal for driving and injecting and adding sodium bromide into the water supply pipe 106, and similarly driving the injection pump 141 to inject and add sodium hypochlorite into the water supply pipe 108 is output.

Then, by injecting and adding the sodium bromide and sodium hypochlorite, urea decomposition in the water to be treated is carried out in the reaction tank 107 by the reactions of the above-mentioned formulas (2) and (3). The reaction tank 107 has a tank volume designed so that the water to be treated can be retained for a sufficient time (for example, 1 to 3 hours) required for urea decomposition depending on the concentration of these agents to be added. .

Test Example 1 The following synthetic water was used as the water to be treated, which was placed in a beaker having a capacity of 5 liters, and the urea concentration in the water to be treated when urea decomposition was carried out under the following conditions with stirring: A test for measuring the change was conducted, and the results are shown in FIG. The urea concentration was obtained by measuring the TOC of the water to be treated and converting from that value.

Water to be treated: electric conductivity 1.0 μS / cm,
The reagent urea was added to pure water with a TOC concentration of 0.02 mg / liter to a concentration of 5 mg / liter, and
PH 7.0 by addition of buffer solution (neutral phosphate solution)
Adjusted to.

Sodium bromide injection Injection amount: An injection amount of 65 mg / liter was added to the water to be treated.

Sodium hypochlorite injection amount: An amount of 78 mg / liter was added by injection to the water to be treated.

Test Example 2 The same conditions as in Test Example 1 except that the sodium bromide of Test Example 1 was not injected and added, but sodium hypobromite was added by 60 mg / liter instead of sodium hypochlorite. The urea decomposition test was carried out in Fig. 5 and the results are shown in Fig. 5.

Test Example 3 The same as Test Example 1 except that the injection of sodium bromide in Test Example 1 was not performed, and that 125 mg / liter of sodium hypobromite was added by injection instead of sodium hypochlorite. A urea decomposition test was conducted under the conditions, and the results are shown in FIG.

Test Example 4 (Comparative Test Example) The same conditions as in Test Example 1 except that the injection addition of sodium bromide in Test Example 1 was not performed and the injection addition amount of sodium hypochlorite was 150 mg / liter. A urea decomposition test was conducted in Table 1 and the results are shown in FIG. 6 together with Test Example 3.

As can be seen from FIGS. 5 and 6 showing the results of these test examples 1, 2, 3 and 4, in test example 1, the urea concentration gradually decreased with time due to the injection addition of sodium hypochlorite. Then, after 120 minutes, the urea concentration was 0.0
It became stable at 05 mg / liter. Further, even when 60 mg / liter of sodium hypobromite in Test Example 2 was added by injection, the same urea decomposition as in Test Example 1 was performed.

In addition, in Test Example 3 in which the injection amount of sodium hypobromite was increased about twice as much as that in the test example, the urea concentration was rapidly lowered by the injection addition of sodium hypobromite.
After 60 minutes, the urea concentration became 0.005 mg / liter and became stable.

On the other hand, in Test Example 4 in which only sodium hypochlorite was added, the urea concentration in the water to be treated was hardly reduced.

Test Example 5 In order to investigate the relationship between the concentration of sodium hypobromite and the rate of urea decomposition, the injection amount of sodium hypobromite added to the water to be treated in Test Example 2 was 30, 60, 125,15
A urea decomposition test was conducted under the same conditions as in Test Example 2 except that the amount was changed to 0,200 mg / liter, and the results are shown in FIG. 7.

From these results, it can be seen that the decomposition rate of urea increases as the amount of sodium hypobromite added increases from the theoretical amount (molar ratio 3) of 30 mg / liter.
That is, when the addition amount of the molar ratio is 3, 9% of urea in the water to be treated is used.
0% is decomposed (in FIG. 7, the urea concentration is 0.5 mg /
It takes 3 hours to reach 1 liter), but the decomposition rate increases with increasing addition amount, and the molar ratio is 15
90% decomposition was reached in about 10 minutes with the addition amount of. Further, even if the molar ratio is further increased, the decomposition rate is not so fast. Therefore, the addition amount of sodium hypobromite is
A molar ratio of 3 to 15 is desirable with respect to urea in the water to be treated.

Test Example 6 In the method of Test Example 1 using sodium bromide and sodium hypochlorite, in order to investigate the relationship between the concentration of sodium bromide and the rate of urea decomposition, the water to be treated in Test Example 1 above was examined. A urea decomposition test was carried out under the same conditions as in Test Example 1 except that the amounts of sodium bromide added to and were changed to 8.3, 25, and 50 mg / liter, respectively, and the results are shown in FIG. The concentration of sodium hypochlorite added was fixed at 78 mg / liter.

From these results, it can be seen that even if the concentration of sodium bromide is low, there is no great influence on the decomposition of urea.

Test Example 7 In the method of Test Example 1 using sodium bromide and sodium hypochlorite, in order to investigate the relationship between the concentration of sodium hypochlorite and the rate of urea decomposition, The amount of sodium hypochlorite injected into the treated water was 18.6, 3
A urea decomposition test was conducted under the same conditions as in Test Example 1 except that the respective amounts were changed to 7.3, 62.1, 93.1, and 186.3 mg / liter, and the results are shown in FIG. The concentration of sodium bromide added was fixed at 25 mg / liter.

From these results, in order to achieve a urea removal rate of 90% or more within a reaction time of 3 hours, the amount of sodium hypochlorite added should be 10 or more with respect to urea in the water to be treated. It turns out that it is necessary.

Test Example 8 To examine the relationship between pH and the rate of urea decomposition in the method using sodium bromide and sodium hypochlorite of Test Example 1, 25 mg / liter of sodium bromide and 62 mg of sodium hypochlorite were used. / Liter is constant and the pH of the water to be treated is 4,
A urea decomposition test was carried out under the same conditions as in Test Example 1 except that each of 6, 7, 8, and 9 was replaced, and the results are shown in FIG.

From these results, the decomposition reaction of urea in the case of using sodium bromide and sodium hypochlorite is faster on the acidic side than on the alkaline side, and the optimum pH is at reaction time 3
Since a urea culture ratio of 90% or more can be obtained within the time, it can be seen that pH 8 or less is preferable. However, as described above, when the reaction pH is less than 4, there is an adverse effect that the hypobromite ion is gasified due to the addition of the above-mentioned agent, which is not preferable.

Example 2 In this example shown in FIG. 3, a urea decomposing means of decomposing urea in water to be treated by injecting and adding sodium bromide as an alkali bromide and ozone was used to produce primary pure water. It shows an example of an ultrapure water production system provided in the system.

The pretreatment apparatus 1 in this example comprises a pH adjusting tank 101, a hydrochloric acid storage tank 102 for injecting hydrochloric acid into the pH storage tank, a caustic soda storage tank 103 for injecting caustic soda, and a coagulant storage tank 104 from the middle. Water pipe 10 for injecting a coagulant and sending water to be treated to the coagulation filter 105
6, the coagulation filter 105 for solid-liquid separation of coagulation flocs,
An activated carbon tower 109 is provided, and such a configuration is known as a pretreatment device in a conventional ultrapure water production system.

Then, in the pretreatment apparatus 1 of this example, it is continuously measured whether or not urea is contained in the raw water by taking in water through the branch pipe 122 for taking in part of the raw water. A urea monitoring device 120 is provided, and a control device 121 for controlling injection and addition of soda bromide and ozone, which will be described later, is additionally provided by a signal from the urea monitoring device 120.

In the above-mentioned structure, the pretreatment device 1 is not provided with a urea decomposition agent injection and addition means for urea decomposition treatment, and is not provided with the reaction tank 107 for urea decomposition. The configuration is the same as that of the first embodiment except for.

Further, the primary pure water producing apparatus 2 of this example has an ion exchange apparatus 207 for removing ions in the water to be treated fed from the pretreatment apparatus 1, and an ion exchange apparatus 207 from this ion exchange apparatus 207 via a water pipe 209. A reaction tank (tank-type reaction water passage) 208 to which treated water is sent, an injection pump 131 for injecting and adding sodium bromide from a sodium bromide solution storage tank 130 in the middle of a water supply pipe 209, and an ozone generator 150. Control valve 151 for injecting and adding ozone from the above into the reaction tank 208
And an exhaust ozone decomposing device 210 such as an activated carbon tank for decomposing residual ozone contained in water to be treated after urea decomposition
And an ion removing device 21 for removing ions in the water to be treated
It consists of one.

Then, when the urea monitoring device 120 detects that the raw water contains urea, the control device 121, the soda bromide injection pump 131, the ozone generator 150, and the ozone injection addition device are used. Control valve 15
1 is driven to inject these urea decomposers.

In the reaction vessel 208 of this example, the residence time of the water to be treated was 180 minutes.

Example 3 This example shown in FIG. 4 is characterized in that a high-pressure ultraviolet irradiation lamp (ultraviolet irradiation lamp for irradiating ultraviolet rays having a main wavelength of 365 nm) 212 is provided in the reaction tank 208 of the above-mentioned Example 2, The other configuration is exactly the same as that of the second embodiment.

In the ultrapure water production system of this example having such a configuration, since ozone is used as the oxidant, the ion load on the equipment in the subsequent stage is higher than that in the case where sodium hypochlorite is used. It is preferable because it is reduced, and the effect that the organic substances other than urea are simultaneously decomposed by the cooperation of the excess ozone and the ultraviolet rays.

Test Example 9 A test was carried out using the same synthetic water as in Test Example 1 to measure the change in the urea concentration in the water to be treated when the urea decomposition treatment was carried out under the following conditions. The results are shown in FIG. Indicated. Also, for comparison reference, 60 m of sodium hypobromite in the above Test Example 2 was used.
The results of adding g / l by injection are repeated.

Sodium bromide injection Injection amount: An injection amount of 25 mg / liter was added to the water to be treated.

Amount of ozone injected: An amount of 75 mg / liter was injected and added to the water to be treated.

From the results shown in FIG. 11, it is understood that the urea contained in the water to be treated is efficiently decomposed by injecting alkali bromide and ozone into the water to be treated, and the structure shown in FIG. 4 is also understood. As can be seen, the excess ozone can be removed easily and there is no problem of increasing the salt load on the ion removing means of the ultrapure water production system.

Test Example 10 Reaction tank 10 in the case where urea was decomposed under the following conditions using industrial water as raw water in the ultrapure water production system having the configuration shown in FIG.
A test for measuring the urea concentration in the water to be treated at the 7th outlet was conducted.

Raw water Flow rate: 1.0 m ³ / H Water quality: Electrical conductivity 180 μS / cm, pH 6.0, TO
C 846 ppb In addition, urea was externally added to the raw water so that the concentration was 5 mg / liter.

Sodium bromide injection Injection amount: An amount of 50 mg / liter was added to the water to be treated.

Addition of Flocculant Flocculant: PAC (polyaluminum chloride) Addition amount: 20 mg / liter Sodium hypochlorite Injection amount: 50 mg / liter was added to the water to be treated.

Reaction tank capacity: 2 m ³ Retention time of treated water: 120 minutes From the start of urea addition, urea was detected by the urea monitoring device 120, and injection and addition of sodium bromide and sodium hypochlorite were started. As a result, the urea concentration at the outlet of the reaction tank was 0.1 mg.
/ Liter or less.

[0081]

Industrial Applicability According to the present invention, it is possible to provide a method and an apparatus capable of producing highly purified ultrapure water in which the concentration of organic substances is further reduced, including urea, which has been difficult to remove in the past. effective.

Further, since the present invention uses a chemical method, compared with the conventionally proposed biochemical method for removing urea, the urea concentration of the raw water in a short-term temporary and seasonal This method has the feature that it can easily cope with rises, and this biochemical urea removal method requires only permanent equipment that is not easy to maintain and manage. There is an advantage that an extremely excellent effect that urea can be easily removed can be obtained.

Furthermore, the present invention does not require a conventional enzyme carrier or a water-passing device for the same, and does not require backwashing for clogging. Therefore, operation and management of equipment for urea removal are not required. The effect is that it is extremely easy.

Further, according to the present invention, by using the monitoring device for detecting the increase of the urea concentration in the raw water, the process by the device attached to the urea removal can be operated temporarily and in a short period of time. .

Furthermore, it is possible to employ a structure in which the processing means for detecting the increase in the urea concentration and then removing the urea is activated, whereby the high-purity water that has undergone multi-step processing is wasted. The advantage of being able to build equipment to be used as water without needing is obtained in particular in the field of semiconductor manufacturing, etc. by means of equipment that can continuously produce high-purity water called so-called ultrapure water. Since the indispensable cleaning water can be provided without stagnation, there is an extremely excellent effect that the semiconductor manufacturing can be continuously performed without stopping the operation.

Further, according to the inventions of claims 15 to 18 of the present application, an increase in the concentration of urea contained in the raw water can be detected rapidly, and therefore, the ultrapure water produced by performing the multi-step purification treatment can be effectively used. In particular, the effect of surely preventing the leakage of urea can be obtained. By using this monitoring system, the increase of the raw water urea concentration can be monitored mechanically and automatically. Therefore, as in the present invention, the urea decomposing agent is added temporarily or in the short term to decompose urea. In the method of implementing, the significance of providing this monitoring system is extremely significant.

[Brief description of drawings]

FIG. 1 is a flow chart showing a schematic configuration of an ultrapure water production system according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining details of the configuration of the urea monitoring device of FIG.

FIG. 3 is a flowchart showing an outline of the configuration of an ultrapure water production system according to Example 2 of the present invention.

FIG. 4 is a flow chart showing a schematic configuration of an ultrapure water production system of Example 3 of the present invention.

FIG. 5 is a diagram showing the results of Test Examples 1 and 2.

FIG. 6 is a diagram showing the results of Test Examples 3 and 4.

FIG. 7 is a diagram showing the results of Test Example 5;

FIG. 8 is a diagram showing the results of Test Example 6;

FIG. 9 is a diagram showing the results of Test Example 7.

FIG. 10 is a view showing the results of Test Example 8.

FIG. 11 is a view showing the results of Test Example 9.

[Explanation of symbols]

1 ... Pretreatment device, 2 ... Primary pure water production device, 3 ...
..Subsystem, 101 ... pH adjusting tank, 102 ...
..Hydrochloric acid storage tank, 103 ... caustic soda storage tank, 104 ...
..Coagulant storage tank, 105 ... Coagulation filter, 106 ...
-Water pipe, 107 ... Reaction tank, 108 ... Water pipe,
109 ... Activated carbon tower, 110 ..., 120 ... Urea monitoring device, 121 ... Control device, 122 ... Branch pipe, 1201 ... Ion removal device, 1202 ...
TOC meter, 130 ... Sodium bromide solution storage tank, 131.
..Injection pump, 140 ... Sodium hypochlorite solution storage tank, 141 ... Injection pump, 150 ... Ozone generator, 151 ... Control valve, 201 ... Ion exchange device, 202. ..Reverse osmosis membrane device, 203 ... Primary pure water tank, 207 ... Ion exchange device, 208 ... Reaction tank, 209 ... Water pipe, 210 ... Waste ozone decomposing device, 211 ...・ Ion removal device, 212 ... High-pressure ultraviolet irradiation lamp.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 1/42 C02F 1/42 A 1/44 1/44 J 1/78 1/78 9/00 502 9/00 502F 502J 502N 502R 503 503B 504 504B 504C 504D

Claims (18)

[Claims] 1. Fine particles, ions, organic matter in the water to be treated,
A method for producing ultrapure water by performing a multi-step purification treatment for removing bacteria and gas, wherein hypobromite, alkali bromide and hypochlorous acid are produced under the condition that the pH of the water to be treated is 4-8. A method for producing ultrapure water, which comprises adding salt to decompose urea in the water to be treated. 2. The method for producing ultrapure water according to claim 1, wherein the hypobromite is sodium hypobromite. 3. The method for producing ultrapure water according to claim 1, wherein the hypochlorite is sodium hypochlorite. 4. The ultrapure amount according to claim 1, wherein the amount of hypobromite added to the water to be treated is 3 to 90 in molar ratio with respect to urea in the water to be treated. Water production method. 5. The ultrapure water according to claim 4, wherein the amount of hypobromite added to the water to be treated is 3 to 15 in terms of molar ratio to urea in the water to be treated. Production method. 6. The ultra pure material according to claim 1 or 3, wherein the amount of hypochlorite added to the water to be treated is 10 to 2000 with respect to the urea in the water to be treated. Water production method. 7. The ultrapure water according to claim 6, wherein the amount of hypochlorite added to the water to be treated is 30 to 600 molar ratio to urea in the water to be treated. Production method. 8. Fine particles, ions, organic matter in the water to be treated,
A method for producing ultrapure water by performing a multi-step purification process for removing bacteria and gas, wherein urea in the water to be treated is added by adding alkali bromide and ozone under the condition that the pH of the water to be treated is 4 to 10. A method for producing ultrapure water, which comprises decomposing. 9. The method for producing ultrapure water according to claim 1, wherein the alkali bromide is potassium bromide or sodium bromide. 10. A urea decomposition treatment means is provided at any position of an ultrapure water production system equipped with multi-stage treatment means for removing fine particles, ions, organic substances, bacteria and gases in the water to be treated, The urea decomposition treatment means is configured to add a urea decomposition agent addition means for decomposing urea in the water to be treated, and a water passage time sufficient to decompose all urea in the water to be treated following the addition position of the addition means. Equipped with a set water passage for reaction,
An apparatus for producing ultrapure water, characterized in that an ion removing means is provided at a stage subsequent to the water passage for reaction. 11. The urea decomposing agent added by the adding means according to claim 10, (1) hypobromite,
(2) Alkali bromide and sodium hypochlorite, and (3) Alkali bromide and ozone. 12. The ultrapure water production system according to claim 10, wherein the ion removing means is an ion exchange device or a reverse osmosis membrane treatment device. 13. The activated carbon tank for removing a urea decomposing agent according to claim 10, wherein an activated carbon tank for removing a urea decomposing agent is provided between the reaction water passage that follows the addition position of the adding means and the ion removing means. Characteristic ultrapure water production equipment. 14. An ultrapure water production apparatus comprising a raw water pretreatment apparatus, a primary pure water production apparatus, and a secondary pure water production apparatus, wherein the ultrapure water production apparatus is provided at any position upstream of the secondary pure water production apparatus. Item 10. An ultrapure water production system provided with the urea decomposition treatment means according to Item 10. 15. A urea decomposition treatment means is provided at any position of an ultrapure water production system equipped with multi-stage treatment means for removing fine particles, ions, organic substances, bacteria, and gases in the water to be treated. An apparatus for producing ultrapure water, comprising a urea monitoring device for continuously detecting the urea concentration in the water to be treated at an upstream position of the urea decomposition treatment means. 16. The urea monitoring device according to claim 15, wherein the branch pipe branches from the water passage to continuously take in the water to be treated, and an ion removing means for removing ions contained in the water to be treated. An ultrapure water production system comprising TOC measuring means for measuring total organic carbon (TOC) contained in water to be treated after removal of ions. 17. The urea monitoring device according to claim 15 or 16 is provided in the middle of a water passage extending from the raw water intake to the urea decomposition treatment means according to any one of claims 11 to 15, and the urea decomposition device is provided. The water passage length from the means to the urea monitoring device is set to be longer than the time required for the treated water to pass through the water passage, longer than the time required for detecting the urea concentration by the urea monitoring device. Ultrapure water production equipment that does. 18. The device according to claim 17, further comprising means for detecting an increase in urea concentration by the urea monitoring device and outputting a signal, and drive control means for receiving the signal and starting the operation of the urea decomposition processing means. An ultrapure water production system characterized in that