JPH05237497A - Pure water preparation - Google Patents

Abstract

PURPOSE:To prepare pure water with high purity with which water soluble substances are removed efficiently and thus electronic devices are cleaned to high cleanness by carrying out sterilization for raw water, adjusting the pH, treating for flocculation and precipitation for the water, and then carrying out ion-exchange treatment. CONSTITUTION:Impurities in raw water such as surfacial flowing water, river water, underground water, or mixture of them are removed and thus pure water is prepared. At that time, to prepare pure water, chlorine agent is added to the raw water in the sterilization process 100 to sterilize the water. Then, the sterilized object water for treatment is adjusted to be pH 5.4-5.8 in the pH adjusting process 200. Next, a flocculant is added to the pH-adjusted object water for treatment to coprecipitate humic acid and the salts and remove them in the flocculation and precipitation process. Finally, the ions in the object water for treatment which is treated for flocculation and precipitation are removed in ion-exchange treatment process 400. As a result, water soluble substances, etc., are removed efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing pure water, and more particularly, to a pure water for obtaining high-purity ion-exchanged pure water from surface water, river water or ground water, or raw water consisting of mixed water thereof. Water production method.

[0002]

2. Description of the Related Art Normally, ground water and surface water are used as raw water for producing pure water. That is, when producing ion-exchanged pure water, the raw water often uses ground water such as well water, surface water, river water, or a mixture of these. Since such raw water contains various impurities,
The treated water from which these impurities have been removed by various treatment methods is subjected to ion exchange treatment to produce pure water.

Conventionally, in the production of pure water using ion exchange, groundwater or surface water is used as raw water. 5ppm to 10pp for pretreatment to remove major impurities in the raw water
The method of coprecipitation in which the pH of the water to be treated is adjusted to 6.5 to 7.8 to precipitate the aluminum as its hydroxide and at the same time main impurities in the raw water are coagulated and removed by aggregation. Is used.

Incidentally, since such a conventional method for producing pure water is well known, no reference is given thereto.

[0005]

In the above prior art, when river water and surface water are used as raw water for producing pure water by ion exchange, among the various impurities contained in the raw water, particularly humic acid is used. When the amount of these impurities and their salts are large, the desired amount cannot be removed only by coagulating and precipitating these various impurities and aluminum, which is a polyaluminum chloride salt added as a coagulant for removing the impurities, as hydroxides.

That is, neither the various impurities contained in the raw water as the water to be treated nor the aluminum as the aggregating agent are sufficiently coprecipitated and removed as hydroxides, and in the past, the pH at the time of aggregating and precipitating the water to be treated was not increased. Since the value is as high as 6.5-7.8,
A part of the generated aluminum hydroxide precipitate is dissolved in the water to be treated and atomized at the same time, and further, aluminum ions generated by the dissolution of the aluminum hydroxide precipitate and impurities contained in the water to be treated. It reacts with humic acid to form a water-soluble substance that cannot be removed by the reverse osmosis membrane or the ion exchange resin in the subsequent treatment.

As a result, there is a problem that the reverse osmosis membrane and the ion exchange resin are heavily loaded, and pure water having a desired water quality cannot be produced. The object of the present invention is to eliminate the problems of the above-mentioned conventional techniques when surface water, river water or ground water, or a mixed water thereof is used as raw water, and is required for manufacturing electronic devices such as semiconductor manufacturing and cathode ray tube manufacturing. It is to provide pure water of desired water quality.

[0008]

To achieve the above object, the present invention provides a pure water for removing impurities in raw water consisting of surface water, river water or ground water, or a mixed water thereof. In the water manufacturing method, a sterilization stage 100 including a step of sterilizing the raw water by adding chlorine, and a pH of the water to be treated that has passed through the sterilization stage 100
PH adjusting stage 200 for adjusting the value to 5.4 to 5.8, and flocculating and precipitating stage for coprecipitating and removing humic acid and its salts together by adding a flocculant to the water to be treated which has passed through the pH controlling stage 200. It is characterized by including at least 300 and an ion exchange processing stage 400.

Further, the present invention is a pure water production method for obtaining pure water by removing impurities in raw water consisting of ground water, surface water, or a mixed water thereof, in which sodium hypochlorite is added to the raw water. The sterilization step of obtaining the treated water sterilized by the method, the pH adjustment step of adding hydrochloric acid to the treated water that has undergone the sterilization step to adjust the pH value to 5.4 to 5.8, and the pH adjustment 75 ppb-100 for treated water
a precipitation reaction step of adding ppb polyaluminum chloride to co-precipitate and remove humic acid and salts thereof in the water to be treated together with other impurities as hydroxide of aluminum; and water to be treated after the precipitation reaction step An adsorption step of adsorbing and removing the supernatant water by using either or both of activated carbon and a reverse osmosis membrane, and an ion exchange treatment step of removing positive and negative ions in the water to be treated after the adsorption step by an ion exchange resin, A fine foreign matter removing step of removing fine foreign matter by passing the water to be treated after the ion exchange treatment through an ultrafine pore filter.

A feature of the present invention is a structure having another pH adjusting step of adjusting the pH value of the supernatant water in the precipitation reaction step to the range of 5.4 to 5.8 again if necessary. Further, the present invention is characterized in that N of the trace amount of impurities contained in the pure water that has passed through the step of removing the fine foreign matter in the manufacturing step.
It is intended to produce pure water in which 10 to 50,000 fine particles of 0.01 μm to 0.1 μm diameter of a, Si, Al, Ca, Mg-based compound and the compound of the element and the organic material-based are per 1 ml. Characterize.

[0011]

[Function] From 75 ppm to 10% of treated water obtained by sterilizing raw water
Before adding 0 ppm of polyaluminum chloride, the pH value of the water to be treated is adjusted to 5.4 to 5.8, polyaluminum chloride is added as a coagulant, and if necessary, N1 (Olflock) is added as a coagulant aid. (Organo Co., Ltd. trade name) is added to increase the size of the agglomerates, and humic acid and other impurities are precipitated together as agglomerates of aluminum hydroxide.

Among the various impurities in the water to be treated, the aggregating agent (and the coagulant aid), in particular, makes humic acid in the form of water-insoluble humic acid-aluminum, and the content of humic acid in the water to be treated is approximately 50%. A considerable amount is coprecipitated with the precipitated particles of aluminum hydroxide. Then, activated carbon or reverse osmosis membrane (R
The water to be treated is passed through OF), plus ions (cations) and minus ions (anions) are removed by an ion exchange resin, and if necessary, cation / anion co-removal treatment is performed.

Finally, by passing through a micropore filter such as a Millipore filter (trade name), Na, Si, Al, Ca, Mg-based compounds and the above-mentioned elements out of the trace impurities contained in pure water. 0.01μ of compounds with organic compounds
10 to 5 fine particles with a diameter of m to 0.1 μm per 1 ml
Pure water of 0000 can be obtained.

[0014]

Embodiments of the method for producing pure water according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view of a main processing stage for explaining an embodiment of the pure water producing method according to the present invention, in which 100 is a sterilization stage, 200 is a pH adjusting stage, 300 is a coagulating sedimentation stage, and 400 is an ion. It is an exchange processing stage.

In this embodiment, in the sterilization stage 100, sodium hypochlorite (NaOCl) is added as a chlorinating agent to raw water consisting of surface water, river water or ground water, or mixed water thereof, and NaOCl + H ₂ O → The chlorine gas (Cl ₂ ) generated from NaOH + Cl ₂ kills (or suppresses the reproduction of) bacteria in the raw water. When tap water such as public tap water is used as the raw water, the sterilization treatment can be omitted because the raw water supplied has already been sterilized.

The water to be treated which has passed through the sterilization stage 100 is
The pH value is adjusted in the range of 5.4 to 5.8 by the pH adjusting stage 200. Conventionally, since the pH value of this treated water is adjusted to 6.5 to 7.8, a humic acid-water-soluble humic acid-aluminum complex salt is formed, so that the amount of humic acid removed is the amount of humic acid in the raw water. The amount of the humic acid-aluminum complex salt cannot be removed even by ion exchange treatment, and the desired amount of ion-exchanged pure water cannot be obtained.

Next, in the coagulation-sedimentation treatment stage 300, the PAC, that is, polyaluminum chloride (((a), is added as a coagulant to the water to be treated whose pH value has been adjusted to the range of 5.4 to 5.8 by the pH control stage 200. AlCl _{3) n: n} = 5~1
5) is added to coprecipitate and remove humic acid and its salts together. At this time, if necessary, an agglomeration lump is enlarged by adding an aggregating aid.

In the ion exchange treatment stage 400, the ions in the supernatant water of the precipitation tank in the flocculation and precipitation treatment stage 300 are removed by an ion exchange resin. At this time, if necessary, the pH of the supernatant water is readjusted to 5.4 to 5.8. By passing through each of the treatment stages described above, it becomes possible to produce high-quality pure water having a desired water quality.

FIG. 2 is an overall process diagram for explaining an embodiment of the pure water producing method according to the present invention, in which 1 is raw water, 2 is chlorine adding process, 3 is sterilized raw water, that is, process water is stored. 4 is a pH adjusting step, 5 is a PAC (aggregating agent) adding step, 5'is an N1 (aggregating auxiliary) adding step which is adopted as needed, 6 is a precipitation reaction step, 7 is a supernatant water storing step, 7 '
Is another pH adjusting step that is added as necessary, 8 is an adsorption step, 9 is a cation removal step (plus ion removal step), 10 is an anion removal step (minus ion removal step), 11 is cation / anion co-removal Step 12 is a fine foreign matter removing step, and 13 is manufactured pure water. In the figure,
The same reference numerals as in FIG. 1 correspond to the same parts.

In the figure, when public tap water or the like is used as raw water, the sterilization step 2 can be omitted. 3, 4 and 5 are explanatory views showing the filter residue state on the micropore filter (Millipore filter: product name) used in the step of removing fine foreign matter in FIG. 2, which is manufactured according to the processing conditions in FIG. Indicates the quality of pure water.

The pure water production process of FIG. 2 will be described below with reference to FIGS. In FIG. 2, raw water 1 is sterilization process 2
Then, sodium hypochlorite (NaOCl) is added as a chlorine agent to sterilize. The sterilized water to be treated is temporarily stored in the storage tank (storage step 3), and the pH is adjusted in the pH adjustment step 4.
The H value is adjusted. treated water after pH adjustment, PAC in PAC process _{((AlCl 3) n: n} = 5~15)
Is added to cause coagulation and precipitation together with some impurities of the water to be treated as a precipitate of aluminum hydroxide according to the following reaction formula. (AlCl ₃ ) _n + H ₂ O → H ₂ O + 3Cl ₂ + (OH ⁻ ) → [Al ³⁺ (H ₂ O) ₃ (OH ⁻ ) ₃ ] ⁰ First, the water to be treated in FIG. The pH value of the water to be treated that has been sterilized by the sterilization stage 100 in FIG. 1) is adjusted to 6.5 to 7.8 by addition of hydrochloric acid, and then 5 to 10 ppm of polyaluminum chloride is added as a coagulant, followed by hydroxylation. Ion exchange treatment consisting of adsorption step 8 → cation removal step 9, anion removal step 10 and cation / anion co-removal step 11 of FIG. When treated in the step 400, the state of impurities adhering to the Millipore filter (trade name) in the fine foreign matter removing step 12 is visually confirmed in the pores 31 of the pole pore filter 30 made of the Millipore filter (trade name) as shown in FIG. Clog Foreign matter 32 is left can not be obtained pure water quality to be desired.

Then, in the pH adjusting step 4 of FIG. 2, the pH value of the water to be treated is adjusted to the range of 5.4 to 5.8 by adding hydrochloric acid, and then in the precipitation reaction step 6, 20 ppm of polyaluminum chloride as a coagulant is added. The same adsorption step 8 → cation removal step 9, anion removal step 10, cation / anion co-removal step 11 in which 50 ppm was added and the supernatant water after coprecipitation with removal of some impurities in the treated water as a precipitate of aluminum hydroxide was removed
When treated with the ion exchange treatment stage 400 consisting of, the state of impurities adhered to the very fine pore filter consisting of the Millipore filter (product name) in the fine foreign matter removing step 12 consists of the Millipore filter (product name) as shown in FIG. Foreign substances that cause clogging of the polar pores 31 of the polar pore filter 30 are reduced, and the quality of pure water is greatly improved. However, the foreign matter 33 that clogs the pores 31 of the extremely fine pore filter 30 still remains.

As a result of analyzing the foreign matter that causes the clogging of the extra fine pore filter 30, the foreign matter is a water-soluble reaction product of humic acid which is an impurity in the treated water and polyaluminum chloride added as a coagulant. Humic acid-aluminum complex salt. Based on this fact, the pH value of the treated water was adjusted to 5.4 to 5.8 by adding hydrochloric acid in the pH adjusting step 4 of FIG. Humic acid-aluminum, which is a reaction product of humic acid which is an impurity in treated water and polyaluminum chloride added as a coagulant, at the same time to form a large and heavy particle precipitate of aluminum hydroxide by adding -80 ppm. The supernatant water obtained by coprecipitating and removing aluminum hydroxide as a water-insoluble substance is the same as the above adsorption step 8 → cation removal step 9, anion removal step 10, and cation / anion co-removal step 11 In the case where the treatment is carried out in accordance with FIG. Foreign matter will not cause clogging in the pores 31 of the polar microporous filter 30 as shown in.

Thus, by adjusting the pH value of the treated water in the pH adjusting step 4 to 5.4 to 5.8, Na, Si, and Al among the trace impurities in the produced ion-exchanged pure water are adjusted. , Ca, Mg-based compounds and compounds of the above-mentioned elements and organic compounds, the number of circular particles having a particle diameter of 0.01 μm to 0.1 μm is 10 to 50,000 per 1 ml of ion-exchanged pure water. The pure water can be stably produced.

FIG. 6 is an explanatory view for verifying the relationship between the pH value of the water to be treated and the chemical species produced by the reaction. The production of aluminum humic acid-aluminum in the coagulation-sedimentation reaction treatment stage of FIG. It is shown in correspondence with the value. As shown in the figure, the amount of Al ³⁺ increases when the pH value of the water to be treated is low or high. When the pH value is in the range of 5.4 to 5.8, A
The amount of l ³⁺ becomes the minimum value (20 ppb) and the removal rate is 9
Reach 9.2%.

FIG. 7 is a graph showing the relationship between the pH value of the water to be treated, the amount of humic acid (TOC) removed by the coagulation-precipitation reaction, and the amount of residual aluminum. The pH value is 5.4 to 5.8.
It is understood that the optimum remaining amount of both can be set by selecting the range of. FIG. 8 is an explanatory view showing a schematic configuration of a pure water production apparatus for carrying out the pure water production method according to the present invention,
301 is a storage tank for water to be treated (here, tap water supplied from public water supply), 401 is a pH adjusting tank, 601 is a precipitation reaction tank, 701 is a supernatant water storage tank, 801 is an activated carbon or reverse osmosis membrane treatment tank, 901 is a cation removal tower, 1001 is an anion removal tower, 1101 is a cation / anion co-removal tower,
Reference numeral 1201 is a filter tank, and 1301 is a pure water storage tank.

In the figure, the pH value of the tap water received in the storage tank 301 is adjusted to pH 5 by adding hydrochloric acid in the pH adjusting tank 401.
Adjust to 4-5.8. The water to be treated whose pH has been adjusted to 5.4 to 5.8 is added with PAC in the precipitation reaction tank 601 (N1 is added if necessary) to cause the humic acid-aluminum aggregation and precipitation described above. The supernatant water of the precipitation reaction tank 601 is temporarily stored in the supernatant water storage tank 701.

This supernatant water is an activated carbon / RO membrane treatment tank 801.
At this point, the adsorption treatment of impurities is performed by the activated carbon or the reverse osmosis membrane (RO membrane), and the cation removal tower 901 is reached. The cation removing tower 901 removes positive ions with an ion exchange resin, and then the anion removing tower 1001 removes negative ions. The remaining positive ions and negative ions are removed by passing through a cation / anion co-removal column 1101.

The water to be treated which has been subjected to the ion exchange treatment is subjected to a treatment for removing minute foreign matters in a filter tank 1201 equipped with a minute filter consisting of a Millipore filter (trade name), and is then stored in a pure water storage tank 1301 as a pure water product. Stored. The pure water stored in the pure water storage tank 1301 is supplied to the manufacturing department of the required electronic device or the like.

By using the pure water produced in this way as water for washing parts such as electronic devices, it is possible to perform cleaning with a high degree of cleanliness.

[0031]

As described above, according to the present invention,
Highly cleanliness can be achieved by using the produced pure water as washing water in the production of semiconductors, cathode ray tubes and other electronic devices. FIG. 9 is an explanatory view showing an enlarged micro region of a cleaning part showing the cleaning effect of pure water manufactured by the present invention in comparison with the cleaning effect of pure water manufactured by a conventional technique. The surface of the component cleaned with pure water manufactured according to the invention, and (b), the surface of the component cleaned with pure water manufactured by the prior art.

As can be seen by comparing FIG. 11A and FIG. 11B, the surface of the component (a) washed with pure water manufactured according to the present invention has the foreign matter shown in FIG. 34 is almost nonexistent. Therefore, by using the pure water produced by the present invention as cleaning water, a high cleanliness of the surface of the cleaning component can be ensured, and the semiconductor, cathode ray tube, and other electronic products using the component can be significantly improved in performance. Also, high reliability can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic view of a main processing stage for explaining a process of an embodiment of a pure water producing method according to the present invention.

FIG. 2 is an overall process diagram illustrating an embodiment of the pure water production method according to the present invention.

FIG. 3 is an explanatory diagram showing a filtration residue state on an ultrafine pore filter used in an ultrafine foreign matter removing step in a pure water producing step.

FIG. 4 is an explanatory diagram showing another filtration residue state on the micropore filter used in the step of removing fine foreign matter in the step of producing pure water.

FIG. 5 is an explanatory diagram showing a filtration residue state on an ultrafine pore filter used in a step of removing fine foreign matter in the step of producing pure water according to the present invention.

FIG. 6 is an explanatory diagram for verifying the relationship between the pH value of the water to be treated and the reaction-produced chemical species.

FIG. 7 is a graph showing the relationship between the pH value of water to be treated, the amount of humic acid (TOC) removed by the coagulation-precipitation reaction, and the amount of residual aluminum.

FIG. 8 is an explanatory diagram showing a schematic configuration of an example of a pure water production apparatus for carrying out the pure water production method according to the present invention.

FIG. 9 is an explanatory view showing an enlarged micro region of a cleaning component showing a cleaning effect of pure water manufactured by the present invention and a cleaning effect of pure water manufactured by a conventional technique.

[Explanation of symbols]

 100 Sterilization stage 200 pH adjustment stage 300 Coagulation sedimentation treatment stage 400 Ion exchange treatment stage 1 Raw water 2 Sterilization process 3 Engraving process 4 pH adjustment process 5 PAC addition process 5'N1 addition process 6 Precipitation reaction process 7 Supernatant water storage process 7 ' pH adjustment step 8 Adsorption step 9 Cation removal step 10 Anion removal step 11 Cation / anion co-removal step 12 Fine foreign matter removal step 13 Pure water

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C02F 1/76 A 9045-4D // C02F 1/52 K 7824-4D (72) Inventor Toshikazu Morishita 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory (72) Inventor Hiromi Kawagoe 3300, Hayano Mobara city, Chiba Prefecture Hitachi, Ltd. Mobara plant (72) Inventor Sumiko Watanabe 3300 Hayano Mobara, Chiba shares Hitachi, Ltd. Mobara factory

Claims (2)

[Claims] 1. A pure water production method for obtaining pure water by removing impurities in raw water consisting of surface water, river water or ground water, or mixed water thereof, and sterilizing by adding a chlorine agent to the raw water. A sterilization stage for treatment, a pH adjustment stage for adjusting the pH value of the sterilized water to be treated to a range of 5.4 to 5.8, and a humin by adding a coagulant to the pH-treated water. A method for producing pure water, comprising a coagulation-precipitation treatment stage for coprecipitating and removing an acid and salts thereof, and an ion exchange treatment stage for removing ions of the coagulation-precipitation-treated water to be treated. 2. A pure water producing method for obtaining pure water by removing impurities in raw water consisting of surface water, river water, ground water, or a mixed water thereof, wherein sodium hypochlorite is added to the raw water. Sterilization step, and adding pH to the sterilized water to be treated
PH adjusting step of adjusting the value in the range of 5.4 to 5.8, and 75 ppb to 100 ppb of the pH-adjusted water to be treated.
A precipitation reaction step of adding polyaluminum chloride to remove co-precipitate humic acid and its salts as aluminum hydroxide with other impurities in the water to be treated; A treatment step of removing clear water using either or both of activated carbon and a reverse osmosis membrane, and an ion exchange treatment step of removing positive and negative ions in the water to be treated after the treatment step through an ion exchange resin, A fine foreign matter removing step of removing fine foreign matter by passing the water to be treated through the ion exchange treatment step through an ultrafine pore filter,
A method for producing pure water, comprising: