JPH09294977A - Water purifying apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high quality purified water efficiently by installing an ultraviolet sterilizer before or behind a means for injecting acid and a dispersant into raw water and treating water discharged from the sterilizer in sequence by passing through a reverse osmosis film separator, a film type degasifier, and a deionizing means. SOLUTION: In the purification of water, RO-concentrated water obtained by RO treating clean water is received by a raw water tank 1, extracted by a pump P1, added with injected acids and a dispersant, and sent to a UV sterilizer 2. The treated water after sterilization treatment is RO-treated in an RO apparatus 3. Part of the concentrated water of the RO apparatus 3 is circulated to the raw water tank 1, the residual part is discharged outside a system, and permeable water is decarbonated by a film type degasifier 4. The treated water of the degasifier 4, after being treated further by a UV sterilizer 5, is deionized by a deionizing means 6. In the water purifying apparatus, the blocking of the RO apparatus 3 and the deionizing means 6 is prevented, and high purity water can be produced efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing pure water, and particularly to a reverse osmosis membrane separation treatment (RO
The present invention relates to an apparatus for efficiently producing high-quality pure water by using concentrated water (hereinafter referred to as “RO concentrated water”) obtained by treatment) as raw water.

[0002]

2. Description of the Related Art In recent years, as an apparatus for producing pure water from clean water, RO water (reverse osmosis membrane separation apparatus) is used to treat clean water without adding chemicals, and the permeated water is passed through an ion exchange resin tower or The thing processed with an electric deionization apparatus is used widely. In this device, when the RO concentrated water discharged from the RO device is discharged to the outside of the system, the water recovery rate is about 60% at most, so from the aspect of effective use of water resources and reduction of wastewater treatment load, etc. It is desired to reuse the RO concentrated water by recovering the RO concentrated water to produce pure water.

Conventionally, when the RO concentrated water is treated, the RO treatment is performed again by using a cellulose acetate RO membrane (CA membrane). In this case, the RO concentrated water is increased in order to increase the recovery rate. An acid and a dispersant are added to the water and water is passed through the RO device to prevent the scale of the RO film from being scaled.

[0004]

Permeated water (hereinafter referred to as "RO permeated water") produced when RO treatment is carried out by adding an acid or a dispersant to RO concentrated water in order to prevent the scale of the RO membrane. .) Becomes acidic at pH 4-5.5. Therefore, this R
O permeated water is water in which bicarbonate ions (HCO ₃ ⁻ ) in water are dissolved as carbon dioxide gas (CO ₂ ), so the load on the electric deionization device and the ion exchange resin tower is too large,
It cannot be processed by an electric deionization device or an ion exchange resin tower.

In order to solve this problem, carbon dioxide gas in the RO permeate water has been removed using various decarbonation devices, but the conventional decarbonation device has the following problems. It was That is, although the vacuum degassing tower and the nitrogen degassing tower are expensive, and the net ring (Raschig ring) decarboxylation tower is inexpensive, viable bacteria are easily proliferated in the accumulated water in the tower.

[0006] In addition, C conventionally used in RO equipment
The film A has relatively high oxidation resistance and a high permissible concentration for residual chlorine, but on the other hand, when chlorine is not present in the system, viable bacteria easily grow, and the ion removal rate, particularly silica removal rate is not sufficient. There are drawbacks.

[0007] The present invention solves the above-mentioned conventional problems and provides an RO
An object of the present invention is to provide a pure water production apparatus capable of efficiently producing high-quality pure water by preventing the generation of scale and the growth of live bacteria by using concentrated water as raw water.

[0008]

The pure water producing apparatus of the present invention is a pure water producing apparatus in which concentrated water produced in a reverse osmosis membrane separation treatment is used as raw water, and means for injecting an acid and a dispersant into the raw water. An ultraviolet (UV) sterilizer provided before or after the injecting means, a reverse osmosis membrane separator for treating the outflow water of the ultraviolet sterilizer, and a membrane for treating the permeated water of the reverse osmosis membrane separator And a deionizing means for deionizing the effluent of the membrane deaerator.

In the pure water producing apparatus of the present invention, an acid and a dispersant are added to the RO concentrated water to prevent the scale, and the UV sterilizer suppresses the growth of viable bacteria to block the RO membrane. To prevent. By demineralizing this water by RO treatment and degassing the RO permeate water, it is possible to decarbonate without growing live cells. By deionizing this degassed water, Pure water of water quality can be obtained.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an apparatus of an embodiment of the pure water producing apparatus of the present invention.

In the pure water producing apparatus of the present embodiment, RO concentrated water obtained by RO treatment of tap water without chemical injection is received as raw water in the raw water tank 1, and this RO concentrated water is pumped by the pump P _1.
, And the acid and the dispersant are injected and water is sent to the UV sterilizer 2.

As the acid, HCl, H ₂ SO ₄ , H ₃ P
O ₄ or the like can be used, and the pH after acid injection is 4.5 to
It is preferable to inject it so as to be about 5.0. Also,
As the dispersant, may be used phosphonic acid drugs such as the injection volume depends on the SiO ₂ concentration of about 1/20 of the SiO ₂ concentration is suitable.

In the UV sterilizer 2, UV irradiation is performed at 0.01 to 0.2 kw per 1.0 m ³ / Hr for sterilization treatment,
The treated water of the UV sterilization treatment device 2 is then subjected to RO treatment by the RO device 3.

In the present invention, the RO film of the RO device 3 may be a CA film which is generally used in the past, but is preferably a polyamide polymer composite film (PA film), more preferably a spiral type PA film. Is advantageous in terms of processing efficiency. According to the PA film, the water quality of the obtained treated water can be improved by about 5 to 10% as compared with the case where the CA film is used.

In this RO device 3, the water recovery rate, that is, R
It is preferable to treat the RO permeated water sampled with respect to the inflow water amount of the O device 3 at 75 to 85% in terms of the balance between the water recovery rate and the quality of the obtained treated water.

A part of the concentrated water of the RO device 3 is circulated to the raw water tank, the rest is discharged to the outside of the system, and the permeated water is then decarbonated by the membrane deaerator 4. An external pressure type hollow membrane is suitable as the degassing membrane of the membrane degassing apparatus 4, and it is preferable to perform the treatment at 0.05 to 0.2 m ² / Hr per 1 m ^{2 of} membrane area.

In the present invention, by the treatment in the membrane type deaerator 4, the conductivity is 2.0 mS / m or less, particularly 1.2 mS / m or less, and the CO ₂ concentration is 10 mg / L or less, especially 5 mg / L or less. It is preferable to carry out the treatment so that water is obtained.

The treated water in the membrane deaerator 4 is then exposed to UV light.
0.01 to 0.2 per 1.0 m ³ / Hr with the sterilizer 5
After UV irradiation at kW and further sterilization treatment, deionization means 6 performs deionization treatment.

This UV sterilizer 5 is not always necessary, but by providing it, the growth of live bacteria in water can be suppressed to a higher degree, and the deionizing means 6 in the subsequent stage can be reliably prevented from being blocked. You can

In the present invention, the deionizing means 6 is composed of an ion exchange membrane, an ion exchange resin outside the ion exchange membrane, and an embedded electrode, and is an electric deionization device for electrically deionizing or an ion exchange resin tower. Can be used. With an electric deionization apparatus, deionization can be performed for a long period of time without performing regeneration or the like. The concentrated water of this electric deionization device is preferably circulated to the raw water tank in order to increase the recovery rate.

On the other hand, in the case of an ion exchange resin tower, it is necessary to regenerate it, but in the pure water producing apparatus of the present invention, the water whose quality has been improved to some extent is treated by the RO apparatus and the membrane deaerator. Because of the treatment, the regeneration frequency is significantly reduced compared to when tap water is treated.

According to the pure water producing apparatus of the present invention as described above, when the RO concentrated water is collected and treated by the RO apparatus and the deionizing means to produce pure water, the scale is produced and the viable bacteria are produced. Therefore, the RO device and the deionization means can be prevented from being blocked, and high-purity water can be efficiently produced without requiring maintenance for a long period of time.

[0024]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 RO concentrated water (1.2 m ³ //) obtained by RO treatment of tap water without adding chemicals by the pure water producing apparatus of the present invention shown in FIG.
hr and water quality are as shown in Table 1. ) Was collected and processed.

HCl was injected as an acid, and 27.5 mg / L of Clifloat D-170 manufactured by Kurita Water Industries Ltd. was injected as a dispersant to adjust the pH to 4.5 to 5. This was a UV sterilizer. After the treatment, the RO treatment was performed, and the RO permeated water was degassed by a membrane degasser and then treated by an electric deionizer.

The specifications and processing conditions of the apparatus used are as follows. The concentrated water of the electric deionizer was circulated in the raw water tank.

UV sterilizer: 2 units NPX1: 0.15kw made by Nippon Photoscience RO device RO membrane: Spiral type PA membrane (FILMTEC made, BW made
30-4040: 6) Permeated water amount: 1.0 m ³ / hr Concentrated water amount: 0.2 m ³ / hr Recovery rate: 83% Membrane-type deaerator Deaerator: External pressure type hollow fiber membrane (Hoechst Celanese) Made, Li
qui-Cel (registered trademark) 5PCM-122: Two in series) Water flow rate: 1.0 m ³ / Hr Vacuum degree: 2.7 kPa Electric deionization device IONPURE (manufactured by Kurita Water Industries Co., Ltd.) Water flow rate: 0. 8 m ³ / Hr Effluent volume: 0.2 m ³ / Hr RO permeated water, membrane deaerator outlet water, outlet deionizer outlet water (treated water) are shown in Table 1.

[0029]

[Table 1]

From Table 1, according to the pure water producing apparatus of the present invention, high quality pure water can be obtained from RO concentrated water, and the amount of waste water is 1.2 m ³ / hr to 0.2 m ³ / hr.
It can be seen that it can be reduced to 1/6.

Comparative Example 1 The same as in Example 1 except that RO permeated water (CO ₂ concentration; 44.7 mg / L) was directly passed through the electric deionization apparatus without installing the membrane degassing apparatus. When treated with water, the specific resistance of the obtained treated water (outlet water of the electric deionization apparatus) was 0.8 MΩ · cm.

Comparative Example 2 When treated in the same manner as in Example 1 except that the UV sterilizer was not installed before the RO device, the treated water was obtained (outlet water of the electric deionization device). The specific resistance was 0.8 MΩ · cm.

Example 2 A treatment was carried out in the same manner as in Example 1 except that the UV sterilizer was not installed in front of the electrodeionization device. The initial specific resistance of (water) was 14 MΩ · cm.

However, in this case, the electric deionization apparatus was contaminated with organic substances, and the water quality gradually deteriorated.

From these results, it can be seen that the water quality is stabilized for a long period of time by providing the UV sterilizer also in front of the electric deionizer.

Example 3 A membrane-type deaerator was used in the same manner as in Example 1, except that a CA membrane (SC-2100 manufactured by Toray Industries, Inc.) was used as the RO membrane of the RO apparatus. The quality of the outlet water is as follows: conductivity: 2.4 mS / m, silica concentration: 8
mg / L, Ca hardness 5 mg / L, CO ₂ concentration 6.9 mg
/ L, and the specific resistance of the obtained treated water (outlet water of the electric deionization apparatus) was 8 MΩ · cm.

From the results of Example 1 and Example 3, R
It can be seen that the PA film is more effective as the O film.

Example 4 A treatment was carried out in the same manner as in Example 1 except that an ion exchange resin tower having the following specifications was provided in place of the electric deionization apparatus. The specific resistance of the outlet water) was 5 MΩ · cm.

Ion exchange resin tower Anion exchange resin (manufactured by Mitsubishi Chemical Corporation, SA-20A)
B) and cation exchange resin (manufactured by Mitsubishi Chemical Corporation, SK-
35:65 mixed bed tower with 1B) (resin amount: 100 L) The regeneration frequency of this ion exchange resin tower is once every 10 to 12 days (10 to 12 days / cycle), and tap water (conductivity:
Regeneration frequency when processing 12.0 to 18.0 mS / m) (once every 1.5 to 2 days (1.5 to 2 days / cycle))
The reproduction frequency was reduced to about ⅕ compared with.

[0040]

As described above in detail, according to the pure water producing apparatus of the present invention, RO concentrated water can be recovered and processed to efficiently produce pure water of high quality.

According to the pure water producing apparatus of the present invention, the RO which has been conventionally discharged from the system for producing pure water without chemical injection.
Since the concentrated water can be recovered to produce high-purity water and reused, it is possible to improve the water recovery rate and reduce the load of wastewater treatment.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a pure water producing apparatus of the present invention.

[Explanation of symbols]

 1 Raw water tank 2, 5 UV sterilizer 3 RO device 4 Membrane type deaerator 6 Deionization means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuro Nakashi 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd.

Claims (1)

[Claims] 1. A pure water production apparatus using concentrated water produced by a reverse osmosis membrane separation process as raw water, means for injecting an acid and a dispersant into the raw water, and ultraviolet rays provided before or after the injection means. A sterilizing device, a reverse osmosis membrane separation device for treating the outflow water of the ultraviolet sterilization device, a membrane degassing device for treating the permeated water of the reverse osmosis membrane separation device, and an outflow water of the membrane degassing device. A pure water production apparatus comprising a deionization means for performing a deionization process.