JP3491328B2 - Ultrapure water production equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrapure water production system,
In particular, the present invention relates to an ultrapure water production system capable of significantly reducing TOC (total organic carbon) in ultrapure water produced from tap water or raw water having a quality similar to that of tap water.

[0002]

2. Description of the Related Art Conventionally, an ultrapure water production system for producing ultrapure water from raw water such as city water, groundwater, and industrial water is basically a pretreatment device, a primary pure water production device, and a secondary water production device. It consists of pure water production equipment. Among them, the pretreatment device is
Floating and filtering equipment. The primary pure water production system has 2
A reverse osmosis membrane separation device and a mixed bed ion exchange device, or an ion exchange pure water device and a reverse osmosis membrane separation device, and the secondary pure water production device is a low pressure ultraviolet oxidation device,
It is composed of a mixed bed type ion exchange device and an ultrafiltration membrane separation device.

In each of these device units, T in raw water is
It is a reverse osmosis membrane separation device, an ion exchange pure water device, and a low-pressure ultraviolet oxidation device that reduces the OC component by means such as separation, adsorption, and decomposition.

The TOC reduction mechanism in each device unit is as follows.

Reverse Osmosis Membrane Separator: A filtration method using a reverse osmosis membrane, which removes ionic and colloidal TOC.

Ion-exchange deionizer: Removes TOC components adsorbed on or ion-exchanged with ion-exchange resins.

Low-pressure UV oxidizer: TOC is decomposed to organic acid and further to CO ₂ by 185 nm UV emitted from a low-pressure UV lamp. The decomposed organic matter is removed by the ion exchange resin in the subsequent stage. Particularly, it is used for decomposing volatile organic substances.

However, TOC is 2 to 5 ppb in the ultrapure water produced by the above-mentioned conventional ultrapure water producing apparatus.
Exists to some extent.

Among the impurities present in the raw water, the present inventors have found that a substance that cannot be removed by a conventional ultrapure water production apparatus is a urea compound, and that raw water is used as a method for decomposing this urea compound. It was found that direct biological treatment is an effective method, and a raw water pretreatment device including biological treatment means,
An applicant for a patent for an ultrapure water producing apparatus including a primary pure water producing apparatus and a secondary pure water producing apparatus was first filed by the applicant (Japanese Patent Application No.
No. 225681. Hereinafter referred to as "first application". According to the ultra pure water producing apparatus of the above-mentioned prior application, the TOC concentration in the ultra pure water to be produced is greatly reduced as compared with the conventional ultra pure water producing apparatus.

[0010]

However, TOC removal when various raw waters (industrial water, city water, groundwater, etc.) are treated by using the ultrapure water producing apparatus of the above-mentioned prior application provided with biological treatment means. As a result of studying Noh, the present inventor has obtained the following findings. That is, when the water quality of the biologically treated water at the outlet of the biological treatment means was examined, a high decomposition rate (a decomposition rate of over 90% in the usual case) was obtained for urea,
Regarding TOC, the biologically treated water TOC showed a relatively high value of around 200 ppb regardless of the TOC concentration of the raw water, and it was not possible to obtain a biologically treated water having a TOC concentration lower than this.

Therefore, in the ultrapure water producing apparatus of the prior application, in order to obtain treated water of extremely high purity, such as TOC of 1 ppb or less, as the ultrapure water to be produced, the primary pure water provided at the latter stage of the biological treatment means. A TOC treatment device of the water production device and the secondary pure water production device, specifically, a device having high equipment costs and operating costs such as a reverse osmosis membrane separation device, an ion exchange pure water device, and a low pressure ultraviolet oxidation device. Since it is necessary and the TOC load on these devices is large, there is a problem that the operating cost becomes more expensive or the device becomes larger.

The present invention solves the above-mentioned problems of the prior application and provides a pretreatment device in a pretreatment device having a biological treatment means, a primary pure water producing device and a secondary pure water producing device. Equipment such as reverse osmosis membrane separation device, ion exchange pure water device, and low pressure ultraviolet oxidation device by reducing the TOC concentration of the treated water of the above to reduce the TOC load of the primary pure water production device and the secondary pure water production device. It is an object of the present invention to provide an ultrapure water production apparatus that makes it possible to eliminate the need for an apparatus that is expensive in terms of operating costs and operating costs, or to reduce the operating costs and downsize the apparatus.

[0013]

The ultrapure water producing system according to claim 1 comprises a pretreatment device for pretreating tap water or raw water of a quality similar to this, a primary pure water producing device and a secondary pure water producing device. comprising the ultrapure water production system, the pretreatment apparatus, viewed contains a chemical oxidation treatment unit and a biological treatment unit, said chemical oxidation
The treatment means is an acid having means for introducing ozone or hydrogen peroxide.
It is equipped with an elementary dissolution tank, and the biological treatment means uses activated carbon as a carrier.
A biological treatment tank built in is provided, and the oxygen dissolution tank and the
The biological treatment tank is a connecting pipe installed at the top and bottom
It is connected by .

[0014]

The apparatus for producing ultrapure water according to a second aspect of the present invention is the apparatus for producing ultrapure water according to the second aspect, characterized in that the oxygen dissolving tank is provided with an ultraviolet irradiation device therein.

[0016]

The present inventor investigated the residual TOC component in the biologically treated water obtained by passing the raw water through the biologically treated means. As a result, the residual TOC component in the biologically treated water was found to be a biodegradable humic substance. Confirmed the existence of.

Therefore, studies are repeatedly conducted to decompose this humic substance into something that can be biodegradable by some means, and a chemical oxidation treatment means is added to the biological treatment means of the pretreatment device. The ultrapure water production apparatus of the present invention for oxidatively decomposing quality has been found.

By the way, conventionally, in the field of clean water treatment, a method of injecting ozone into raw water and biologically treating the treated water has been widely adopted as a method for decomposing humic substances.

However, in the course of research conducted by the present inventor, the TOC of biologically treated water obtained by simply injecting ozone into a raw water tank using this method and biologically treating it was about 200 ppb It was found that there is almost no difference from the case of not injecting, and the effect of improving the TOC resolution by ozone injection may not be obtained. The present inventors presumed that this is because ozone injected into the raw water contributes to the decomposition of easily biodegradable organic substances and does not effectively contribute to the decomposition of humic acid that is hardly biodegradable.

Therefore, as in the present invention , the biological treatment tank of the biological treatment means and the oxygen dissolution tank of the chemical oxidation treatment means are connected by connecting pipes provided at the upper and lower portions of each tank, and the biological treatment is performed. The effluent water from the tank is sent to the oxygen dissolution tank for treatment, and then returned to the biological treatment tank again for treatment, or the effluent water from the oxygen dissolution tank is fed to the biological treatment tank for treatment and then again. By recycling the biologically treated water such as returning it to the oxygen dissolution tank and oxidizing it, it was possible to efficiently oxidize and decompose humic substances.

Further, although ozone is effective for the oxidative decomposition of humic substances, it has a very strong oxidizing power, and it is necessary to use ozone-resistant materials for the constituent members such as pipes and tanks.

Therefore, as a simple oxidation method other than the method using ozone, the inventor of the present invention provides an ultraviolet oxidation lamp (hereinafter referred to as "UV lamp") in an oxygen dissolving tank as claimed in claim 2 . Thus, it was confirmed that humic substances can be efficiently decomposed.

As described above, according to the ultrapure water producing system of the second aspect , humic substances can be efficiently decomposed without using ozone.

UV lamps are generally classified into low-pressure, medium-pressure or high-pressure lamps depending on the pressure of the enclosed mercury. Of these, the low-pressure UV lamp emits ultraviolet rays with a wavelength of 185 nm for TOC decomposition, so it is not necessary to use an oxidizing agent together, but medium- and high-pressure lamps require injection of an oxidizing agent such as hydrogen peroxide. Become.

[0025]

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

FIG. 1 is a system diagram of pretreatment means showing an embodiment of the ultrapure water production system of the present invention.

In FIG. 1, reference numeral 1 is a raw water tank into which raw water is introduced through a pipe 11. Reference numeral 2 is an upward flow type biological reaction tank (biological treatment tank), and raw water in the raw water tank 1 is introduced to the lower portion of the tank through a pipe 12 equipped with a pump 12A.
Activated carbon 3 is contained as a carrier inside the biological reaction tank 2. Reference numeral 4 is an oxygen dissolution tank, and an ozone injection pipe 5 is provided at the bottom thereof. The biological reaction tank 2 and the oxygen dissolution tank 4 are connected by a connection pipe 13 provided at an upper portion of each tank and a connection pipe 14 having a pump 14A provided at a lower portion of the respective tanks. Is introduced from the upper part of the tank through the connecting pipe 13 into the upper part of the oxygen dissolving tank 4, and the outflow water of the oxygen dissolving tank 4 is introduced from the lower part of the tank through the connecting pipe 14 into the lower part of the biological reaction tank 2. Has been done. Reference numeral 15 is a pipe for taking out the treated water from the oxygen dissolution tank 4.

In the pretreatment means of the present embodiment, tap water or raw water of a quality similar to tap water, concretely, raw water such as industrial water, city water, and groundwater is pipe 11, raw water tank 1 and pipe 12. Is introduced into the biological reaction tank 2 and is subjected to an upward flow biological treatment to biodegrade the biodegradable TOC component such as urea contained therein.

The outflow water of the biological reaction tank 2 is introduced into the oxygen dissolution tank 4 through the pipe 13 and, while descending in the oxygen dissolution tank 4,
Ozone injected from the ozone injection pipe 5 oxidizes and decomposes the remaining TOC component. In this oxygen dissolution tank 4, since the biodegradable TOC component in the raw water has already been almost removed in the preceding biological reaction tank 2, the injected ozone is a biodegradable TOC such as humic substances. It is effectively used as a component and has an efficient oxidative decomposition. Outflow water of the oxygen dissolution tank 4 is introduced into the lower part of the biological reaction tank 2 through the pipe 14 and is biologically treated again. By circulating the biological reaction tank 2, the connecting pipe 13, the oxygen dissolving tank 4, the connecting pipe 14 and the biological reaction tank 2 in this manner, biodegradation of biodegradable TOC components such as urea in raw water, and Oxidative decomposition of bio-degradable TOC components such as humic substances to bio-degradable TOC components and biodegradation of the bio-degradable TOC components proceed efficiently, and these are removed to a remarkably low concentration.

However, from the upper part of the oxygen dissolution tank 4, a part of the liquid in the tank is taken out as treated water through the pipe 15 and is sequentially supplied to the subsequent primary pure water producing apparatus and secondary pure water producing apparatus. To be done.

FIG. 2 is a system diagram of a pretreatment means showing another embodiment of the present invention, in which members having the same functions as those shown in FIG. 1 are designated by the same reference numerals. The pretreatment means shown in FIG. 2 is different from the pretreatment means shown in FIG. 1 in that a UV lamp 6 is attached to the oxygen dissolving tank 4, and other configurations are the same.

In the pretreatment means of this embodiment, the oxygen dissolution tank 4 is used.
In the above, in combination with the UV lamp 6 and the oxidizing agent injected from the injection pipe 5, the biodegradable TOC component is oxidatively decomposed. As a result, H ₂ O ₂ having a weak oxidizing power can be used as the oxidant in the oxygen dissolving tank 4 instead of ozone, and the problem of oxidative deterioration of the material constituting the apparatus is solved.

Even in the case of the pretreatment means shown in FIG. 2, as in the pretreatment means shown in FIG. 1, raw water is used as the biological reaction tank 2, the connecting pipe 13, the oxygen dissolving tank 4, the connecting pipe 14 and the biological reaction tank 2. Is easily biodegradable T such as urea in raw water
The bio-degradable TOC components such as OC components and humic substances are removed to extremely low concentrations. Then, a part of the liquid in the tank is taken out as treated water from the upper portion of the oxygen dissolution tank 4 through the pipe 15 and is sequentially supplied to the subsequent primary pure water producing apparatus and secondary pure water producing apparatus.

The pre-processing means shown in FIGS. 1 and 2 is an embodiment of the present invention, and the present invention is not limited to the illustrated one unless it exceeds the gist.

For example, the biological reaction tank 2 is not limited to the upward flow type, but may be the downward flow type, and similar effects can be obtained. However, in the downward flow type biological reaction tank, it is preferable to use the upward flow type because a treatment such as backwashing is required when the differential pressure rises.

In FIGS. 1 and 2, an oxygen dissolution tank is provided in the latter stage of the biological reaction tank, but when activated carbon is used as a carrier of the biological reaction tank, preferably the biological reaction tank is provided in the latter stage of the oxygen dissolution tank. Is desirable. That is, by providing the biological reaction tank in the subsequent stage, it is possible to prevent the oxidizing agent flowing out from the oxygen dissolution tank from being caught by the activated carbon in the biological reaction tank, and prevent the oxidizing agent from flowing out from the pretreatment means.

In the apparatus for producing ultrapure water of the present invention, the pretreatment apparatus is the pretreatment means shown in FIG. 1 or 2, or the pretreatment means shown in FIG.
Alternatively, in FIG. 2, the biological reaction tank 2 and the oxygen dissolution tank 4 may be replaced with each other, and the biological reaction tank may be arranged only after the oxygen dissolution tank. A coagulation sedimentation device or a coagulation filtration device may be provided before or after the means.

A membrane filter, a sand filter, or the like is preferably provided at the subsequent stage of the biological treatment means as a means for removing the bacterial cells flowing out from the biological treatment means.

In the ultrapure water production system of the present invention equipped with such a pretreatment system, the constitution of the primary pure water production system and the secondary pure water production system provided in the subsequent stage of the pretreatment system is as follows. An example is as in Example 2.

Example 1 Primary pure water production apparatus: first RO membrane separation apparatus → second RO membrane separation apparatus → mixed bed type ion exchange apparatus Secondary pure water production apparatus: low pressure ultraviolet oxidation apparatus → mixed bed type ion exchange apparatus → UF membrane Separation device example 2 Primary pure water production device: Multi-bed ion exchange device-> RO membrane separation device Secondary pure water production device: Low pressure ultraviolet oxidation device-> Mixed bed type ion exchange device-> UF membrane separation device The present invention will be described more specifically with reference to examples.

Example 1 Raw water (Atsugi city water (September 15th to October 22nd, 1993)) by an ultrapure water producing apparatus using the pretreatment means shown in FIG.
Was processed.

The treatment conditions of each tank of the pretreatment means are as follows.

Biological reaction tank: Filler = coal-based activated carbon (“Kuraray Coal KW20 / 4
0 "made by Kuraray) Raw water retention time (HRT) = 30 minutes Circulation LV = 10 to 20 m / Hr Oxygen dissolution tank: Ozone injection amount: shown in Table 1.

The pretreatment apparatus has the following apparatus configuration by incorporating such pretreatment means, and a primary pure water producing apparatus and a secondary pure water producing apparatus having the following apparatus configurations are provided at the subsequent stage of the pretreatment apparatus. The processing was performed according to the device specifications and processing conditions.

Pretreatment device Atsugi City water → Biological reaction tank → Oxygen dissolution tank → Coagulation filtration device Primary pure water production device First RO membrane separation device → Second RO membrane separation device → Mixed bed type ion exchange device Secondary pure water production device Low-pressure UV oxidizer → mixed bed ion exchanger → UF membrane separator operating conditions 1st RO membrane separator: salt removal rate 98% or higher, recovery rate 80
% Second RO membrane separator: Salt removal rate 98% or more, recovery rate 90
% Mixed bed type ion exchange device (primary): Water flow SV10 (H
r ^-1 ) Low-pressure ultraviolet oxidation device: irradiation dose 0.2 KWH / m ³ mixed bed type ion exchange device (secondary): water flow SV60-100
(Hr ⁻¹ ) UF membrane separation device: recovery rate 90 to 95% TOC concentration of pretreated water (outflow water of oxygen dissolution tank) and final treated water (outflow water of secondary pure water production device) was measured, and the result Is shown in Table 1.

[0046]

[Table 1]

Example 2 Raw water (water from Atsugi City (September 15, 1993 to October 22, 1993)) by an ultrapure water production system using the pretreatment means shown in FIG.
Was processed.

The treatment conditions of each tank of the pretreatment means are as follows.

Biological reaction tank: Filler = coal-based activated carbon ("Kuraray Coal KW20 / 4
0 ”made by Kuraray) Raw water retention time (HRT) = 30 minutes Circulation LV = 10 to 20 m / Hr Oxygen dissolution tank: H ₂ O ₂ injection amount: shown in Table 2.

Irradiation dose of medium pressure UV lamp: shown in Table 2.

The pretreatment apparatus has the following apparatus constitution by incorporating such pretreatment means, and the primary pure water producing apparatus and the secondary pure water producing apparatus having the same apparatus constitution as the embodiment 1 are provided at the subsequent stage of the pretreatment apparatus. Was installed and processing was performed under the following apparatus specifications and processing conditions.

The TOC concentrations of the pretreated water (outflow water of the oxygen dissolution tank) and the final treated water (outflow water of the secondary pure water production apparatus) were measured, and the results are shown in Table 2.

[0053]

[Table 2]

From Tables 1 and 2, according to the ultrapure water production system of the present invention, the TOC concentration of the pretreated water can be significantly reduced as compared with the case where the chemical oxidation treatment means is not used. As is clear, it is possible to efficiently obtain high-purity ultrapure water.

[0055]

As described in detail above, according to the apparatus for producing ultrapure water of the present invention, a pretreatment apparatus including a biological treatment means is additionally provided with a chemical oxidation treatment means, so that biodegradable substances such as humic substances are hardly decomposed. By oxidizing and decomposing a volatile substance by the chemical oxidation treatment means, the TOC concentration in the outflow water of the pretreatment device can be remarkably reduced.

As a result, the loads on the primary pure water producing device and the secondary pure water producing device in the subsequent stage are significantly reduced, and the reverse osmosis membrane separation device, the ion exchange pure water device of the primary or secondary pure water producing device, It is possible to eliminate the need for a device such as a low-pressure ultraviolet oxidation device that is expensive in terms of equipment cost and operating cost, or to reduce operating cost and downsize the device.

Therefore, according to the apparatus for producing ultrapure water of the present invention, highly pure ultrapure water can be produced efficiently at low cost.

[0058]

According to the ultrapure water production system of the second aspect , it is possible to effectively perform oxidative decomposition without using ozone, which has a strong oxidative corrosive power, for the device constituent materials.

[Brief description of drawings]

FIG. 1 is a system diagram of pretreatment means showing an embodiment of an ultrapure water production system of the present invention.

FIG. 2 is a system diagram of pretreatment means showing another embodiment of the ultrapure water production system of the present invention.

[Explanation of symbols]

1 Raw water tank 2 Biological reaction tank 3 activated carbon 4 oxygen dissolution tank 6 UV lamp

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C02F 9/00 503 C02F 9/00 503B 504 504A 1/32 1/32 1/72 1/72 Z 101 101 1/78 1 / 78 3/06 3/06 3/10 3/10 A (58) Fields surveyed (Int.Cl. ⁷ , DB name) C02F 9/00 C02F 1/32 C02F 1/72-1/78 C02F 3/00 -3/34

Claims (2)

(57) [Claims] 1. An ultrapure water production apparatus comprising a pretreatment apparatus for pretreating tap water or raw water of a water quality similar thereto, a primary pure water production apparatus and a secondary pure water production apparatus, wherein the pretreatment apparatus is a chemical oxidation processing means and viewing including the biological treatment means, chemical oxidation processing means ozone or introduction hands of hydrogen peroxide
The biological treatment means is provided with an oxygen dissolution tank having stages, and the biological treatment means has activated carbon as a carrier.
The oxygen dissolving tank and the biological treatment tank are provided at the upper part and the lower part, respectively.
An ultrapure water production system characterized by being connected by a connecting pipe provided there . 2. The ultrapure water production system according to claim 1 , wherein the oxygen dissolving tank comprises an ultraviolet irradiation device inside.