JPH05309398A - Apparatus for producing pure water - Google Patents

Abstract

PURPOSE:To continuously and efficiently produce water of high purity over a long period of time, in an apparatus for producing pure water by treating raw water using an RO(reverse osmosis) membrane device and an CDI (electrodialyser), by preventing the deterioration of an RO membrane or the ion exchange resin of the CDI due to dissolved oxygen in raw water, the lowering in the quality of treated water due to the propagation of bacteria, the lowering of the amount of treated water and the clogging of the RO membrane. CONSTITUTION:A raw water deoxidizing means is provided and raw water is successively treated in the order of deoxidizing device (vacuum degassing tower 2) RO membrane device 3 CDI 5. Since the raw water subjected to deoxidizing treatment in the vacuum degassing tower 2 is introduced into the RO membrane device 3, the deterioration of the RO membrane or the iron exchange resin of the CDI 5 due to dissolved oxygen in raw water is prevented. The propagation of bacteria is also suppressed and bacteria trouble such as fouling or the clogging of the RO membrane is also prevented and water of high purity can be efficiently produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pure water producing apparatus,
In particular, the present invention relates to a pure water producing device effective as a water treatment system for medicines and foods.

[0002]

2. Description of the Related Art Conventionally, as a pure water production apparatus, a non-regeneration type ion exchange apparatus loaded with an ion exchange membrane and an ion exchange resin, that is, an electrodialyzer (hereinafter sometimes abbreviated as "CDI") is used. Known (Japanese Patent Laid-Open No. 61-10790)
No. 6). CDI is capable of effective deionization of a wide range of raw water, from large-scale salt removal to purification of manufactured water by reverse osmosis.

[0003] CDI does not require regeneration like ion exchange resins and allows complete continuous water sampling, and has an excellent effect that extremely high purity water can be obtained.

However, the production of pure water by CDI has a drawback that SiO ₂ in raw water is not sufficiently removed. That is, the SiO ₂ removal rate by CDI is relatively high at the initial stage of water flow, but becomes low when the ion exchange resin is saturated by continuing water flow.
Si at 10 to 30 days after passing water at V and current of 0.2A
The removal rate of O ₂ is 30% or less.

The applicant of the present invention has proposed a pure water producing apparatus capable of stably obtaining extremely high-purity treated water by solving the above problems and improving the SiO ₂ removal rate in CDI. An electrodialyzer in which exchange membranes and cation exchange membranes are alternately arranged to alternately form a concentration chamber and a dilution chamber, and the dilution chamber is filled with a mixture of anion exchange resin and cation exchange resin. (CD
In the pure water production apparatus including I), a pure water production apparatus provided with means for weakly acidifying the raw water supplied to the CDI was developed, and a patent application was previously filed (Japanese Patent Laid-Open No. 3-26390).

[0006] According to the pure water production system disclosed in JP-A-3-26390, by raw water was weakly acidified by supplying eluted SiO ₂ ion exchange resin of CDI to CDI, SiO ₂ removal the rate is greatly improved, moreover according to elution of such SiO _2, only the SiO ₂ is removed, an excellent effect that does not adversely affect the other water quality are obtained.

By the way, in the conventional ultrapure water production system, as shown in FIG. 2, raw water (city water, well water, industrial water) is treated in the activated carbon tower 1 and then the reverse osmosis (RO) membrane separation device 3 is used.
At the rear stage of this RO membrane separator, the vacuum degassing tower 2
Alternatively, a deoxygenation device such as a nitrogen degassing tower is installed, and deoxidized treated water is supplied to the ion exchange device 4. In addition, in FIG. 2, the activated carbon tower 1 is provided for removing chlorine and the like in the raw water. That is, the RO used in the primary pure water production system
Since the membrane (polyamide type) is significantly deteriorated by an oxidizing agent, it is necessary to remove residual chlorine contained in raw water such as city water with a reducing agent or activated carbon.

For example, in Japanese Patent Laid-Open No. 26390/1990, an RO membrane separator is provided in front of the CDI to efficiently remove the electrolyte and TOC components in the raw water to reduce the load on the CDI and reduce the treated water. Aiming for high purity, and further C
It is described that it is preferable to decarboxylate the raw water of DI to remove dissolved CO ₃ . A vacuum degassing tower is mentioned as a concrete means for the decarbonation treatment, but degassing is also carried out by vacuum degassing.

[0009]

However, in the conventional system shown in FIG. 2, when the dissolved oxygen in the raw water is saturated, the RO membrane (organic material) of the RO membrane separator is oxidized and deteriorated. The deterioration of the ion-exchange resin of the ion-exchange device caused by the deterioration caused the quality of treated water and the amount of treated water to decrease. Further, since chlorine is removed by an activated carbon tower or the like, microorganisms grow on the RO membrane surface of the RO membrane separation device, which causes problems such as deterioration of treated water quality and membrane clogging. Such a problem was particularly remarkable in a system that supplies hot pure water.

The present invention solves the above-mentioned conventional problems, and in an apparatus for producing pure water by treating raw water with an RO membrane separation apparatus and an ion exchange apparatus such as CDI, an RO membrane and ions produced by dissolved oxygen in the raw water. Prevents deterioration of the ion exchange resin of the exchange equipment, deterioration of the quality of treated water due to the growth of microorganisms, reduction of the amount of treated water, clogging of membranes, etc. An object is to provide a pure water production apparatus that can be produced.

[0011]

A pure water producing apparatus according to claim 1 comprises a membrane separating means for separating raw water by a reverse osmosis membrane, and an ion exchange apparatus for subjecting the permeated water of the membrane separating means to an ion exchange treatment. The water producing device is characterized by being provided with a deoxidizing means for deoxidizing the raw water supplied to the membrane separating means.

A pure water producing apparatus according to a second aspect is the pure water producing apparatus according to the first aspect, wherein the ion exchange apparatus alternately arranges a plurality of anion exchange membranes and cation exchange membranes to form a concentration chamber and a dilution chamber. It is characterized in that it is a non-regeneration type ion exchange device which is formed alternately and in which the anion exchange resin and the cation exchange resin are mixed and filled in the dilution chamber.

[0013]

In the pure water producing apparatus of the present invention, since the raw water deoxidized by the deoxidizing means is introduced into the RO membrane separating means, the deterioration of the RO membrane due to the dissolved oxygen in the raw water and the ions of the ion exchange apparatus such as CDI. The deterioration of the exchange resin is prevented. In particular, during the water passing treatment at a high temperature, the pure water producing apparatus of the present invention can effectively prevent deterioration. Further, the growth of microorganisms is suppressed, microbial damage such as fouling and membrane clogging is prevented, and high-purity pure water can be efficiently produced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing an embodiment of the pure water producing apparatus of the present invention.

The pure water producing apparatus shown in FIG.
Vacuum degassing tower 2, reverse osmosis (RO) membrane separator (hereinafter referred to as "RO
Membrane device ". ) 3 and an electrodialyzer (CDI) 5 mainly. 11 is a pipe for introducing raw water, 12
Is a pipe for supplying the treated water of the activated carbon tower 1 to the vacuum degassing tower 2,
13 is a pipe for supplying the treated water of the vacuum degassing tower 2 to the RO membrane device 3, 14 is a pipe for supplying the treated water of the RO membrane device 3 to the CDI 5, and 15 is a pipe for taking out the treated water (pure water). is there.

In the pure water producing apparatus having the structure shown in FIG.
Raw water such as industrial water, city water, and well water is completely depleted of residual chlorine (usually about 0.5 to 1.5 ppm) in the activated carbon tower 1, and then deoxygenated in the vacuum degassing tower 2. Then R
It is processed by the O film device 3 and supplied to the CDI 5.

The cations such as Na ⁺ in the water supplied to the CDI 5 permeate the cation exchange membrane, and the anions such as Cl ⁻ permeate the anion exchange membrane and are concentrated in the concentration chamber. HCO ₃ ^{− and the} like produced by conversion of CO ₂ also permeate the anion exchange membrane and are concentrated in the concentration chamber. The treated water from which the anions and cations have been removed in this way is C
It is discharged from the DI diluting chamber through the pipe 15, is post-treated as necessary, and is then delivered to the use point.

In the vacuum degassing tower 2, it is preferable that dissolved oxygen (usually about 7 to 8 ppm) in the raw water is treated to 50 ppb or less and other dissolved gases (CO ₂ etc.) are also removed. ..

That is, in producing pure water by CDI,
CO ₂ dissolved in raw water adversely affects the treatment in CDI as described below.

In the electric regeneration by CDI, the balance of all cations and all anions to be adsorbed is preferably 1: 1. When this ratio is significantly deviated, it is presumed that more ions remain without being regenerated and leak into the treated water. When industrial water or the like is used as raw water, the presence of CO ₂ has a great influence in consideration of the balance between the contained cations and anions. Therefore, it is necessary for stabilizing treatment in CDI to reduce CO ₂ contained in raw water as much as possible.

From the above, in the vacuum degassing tower 2, it is preferable to remove CO ₂ dissolved in the raw water.

In the present invention, as the deoxidizing means, an N ₂ deaeration tower, a catalyst resin deaeration tower, etc. can be used in addition to the illustrated vacuum deaeration tower.

In the RO membrane device 3, the electrolyte and TOC components in the raw water can be efficiently removed, and the CDI
The load in 5 can be reduced, and highly purified treated water can be obtained. In the pure water production apparatus of the present invention provided with the RO membrane device 3 as described above, the concentrated water of CDI 5 may be circulated upstream of the RO membrane device 3. In this case, it is possible to reduce the amount of waste water and save the amount of raw water.

As the RO membrane to be mounted on the RO membrane device 3, a usual commercially available membrane such as a polyamide membrane, a cellulose acetate membrane or an aramid membrane can be used.

Further, in the illustrated pure water producing apparatus, CDI was applied as the ion exchange apparatus, but in the present invention,
Cation and anion can be removed by using a conventional mixed bed type ion exchange apparatus. However, it is most advantageous to use CDI because regeneration is unnecessary, continuous water collection is possible, and ion exchange capacity is excellent.

The pure water producing apparatus of the present invention as described above is extremely effective as a water treatment system for pharmaceuticals and foods. That is, in a water treatment system for pharmaceuticals and foods, bacteria are controlled by regular hot water sterilization (60 to 90 ° C). Alternatively, water flow at 50 to 90 ° C. is applied to control bacteria by hot water flow. In this case, since the raw water temperature to be treated becomes high (40 to 90 ° C), RO membrane and C
Since the performance deterioration due to the oxidative deterioration of the ion exchange resin of DI becomes particularly remarkable, the deoxidizing treatment effect of the raw water by the pure water producing apparatus of the present invention is effectively exhibited.

The present invention will be described in more detail with reference to specific experimental examples and comparative experimental examples.

Experimental Example 1 and Comparative Experimental Example 1 Using the pure water producing apparatus (Experimental Example 1) shown in FIG. 1 or the pure water producing apparatus (Comparative Experimental Example 1) shown in FIG. 2, city water (electrical conductivity 200 μs / cm) was performed and changes in water quality with time of treated water (permeated water) of the RO membrane device were examined, and the results are shown in FIG.

As the RO membrane device, NTR-759 (manufactured by Nitto Denko KK) having a polyamide RO membrane was used, and the water passage conditions of the RO membrane device were as follows. Water supply condition Water supply amount: 0.62 m ³ / hr Treated water amount: 0.14 m ³ / hr Water supply: City water pressure: 15 kg / cm ^{2 In} Experimental Example 1, the dissolved oxygen in the raw water was changed by the vacuum degassing tower. Deoxygenation treatment was performed so that the amount was 50 ppb or less.

As is apparent from FIG. 3, in the case of Comparative Experimental Example 1 in which the deoxidation tower is not installed in the preceding stage of the RO membrane device, about 1
After water was passed for 00 days, the electrical conductivity of the treated water increased to 20 μs / cm in front of the RO membrane device, and the water quality clearly showed a tendency to decrease, whereas in Experimental Example 1 in which the deoxidation tower was installed, the electrical conductivity of the treated water was increased. The degree was 10 μs / cm, which was unchanged, and the effect of deoxidation was recognized.

Experimental Example 2 Using the pure water producing apparatus shown in FIG. 1, water temperature of 50 to 60 ° C.
The treatment was performed using oxygen-saturated water having an electric conductivity of 7 μs / cm as raw water. The RO membrane device and the water flow conditions were the same as in Experimental Example 1, and the treatment with the vacuum degassing tower was approximately the same as in Experimental Example 1. As the CDI, 30 anion exchange membranes and 30 cation exchange membranes (about 0.5 m ² per sheet) of polypropylene resin were arranged alternately, and H type strongly acidic anion exchange resin and OH type strongly basic were used. An anion exchange resin mixed at a volume ratio of 40:60 was filled in each of the dilution chambers in an amount of about 30 liters.

The water flow conditions for CDI were as follows. Feed water amount: 0.14 m ³ / hr process water flow rate: 0.12 m ³ / hr concentrated water flow rate: 0.02 m ³ / hr Voltage: examining temporal quality change of the treated water of 18V CDI, Fig Results Four
It was shown to.

Comparative Experimental Example 2 In the pure water producing apparatus shown in FIG. 2, the same raw water treatment as in Experimental Example 2 was performed using CDI as the ion exchange apparatus. The specifications of the RO membrane device and the CDI and the water flow conditions were the same as in Experimental Example 2. The water quality change over time of the treated water of CDI was examined, and the results are shown in FIG.

As is clear from FIG. 4, in Comparative Experimental Example 2 in which the inflow water of the RO membrane device is not deoxygenated, the water quality of the treated water tends to decrease with time, whereas in the front stage of the RO membrane device, In Experimental Example 2 in which a vacuum degassing tower is installed to deoxidize water, there is no change in water quality.

The pure water producing apparatus of Comparative Experimental Example 2 corresponds to the pure water producing apparatus disclosed in JP-A-3-26390, and even if the CDI feed water is degassed, the RO membrane apparatus water supply water is supplied. It is apparent that the pure water producing apparatus described in JP-A-3-26390 that does not degas the water is slightly inferior in the long-term maintenance effect of the treated water quality.

[0036]

As described above in detail, according to the pure water producing apparatus of the present invention, in the RO membrane apparatus and the apparatus for producing pure water by treating the raw water with the ion exchange apparatus such as CDI, Prevents deterioration of treated water quality due to performance deterioration due to oxidative deterioration of ion exchange resin of ion exchange equipment such as RO membrane and CDI, and reduction of treated water quality and treated water quantity due to microbial fouling and clogging of RO membrane, thus achieving high purity It is possible to continuously and stably produce pure water for a long period of time.

[Brief description of drawings]

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

FIG. 2 is a system diagram showing a conventional example.

FIG. 3 is a graph showing the results of Experimental Example 1 and Comparative Experimental Example 1.

FIG. 4 is a graph showing the results of Experimental Example 2 and Comparative Experimental Example 2.

[Explanation of symbols]

 1 Activated carbon tower 2 Vacuum degassing tower 3 RO membrane device 4 Ion exchange device 5 CDI

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C02F 1/44 J 8014-4D 1/469 1/58 T

Claims (2)

[Claims] 1. Membrane separation means for separating raw water by reverse osmosis membrane,
A pure water production apparatus comprising an ion exchange device for ion-exchange treatment of permeated water of the membrane separation means, characterized in that deionizing means for deoxidizing raw water supplied to the membrane separation means is provided. Water production equipment. 2. The pure water producing apparatus according to claim 1, wherein the ion exchange apparatus comprises a plurality of anion exchange membranes and cation exchange membranes alternately arranged to alternately form a concentration chamber and a dilution chamber, A pure water production apparatus, which is a non-regeneration type ion exchange apparatus in which an anion exchange resin and a cation exchange resin are mixed and filled in a dilution chamber.