JP2006281032A - Apparatus and method for treating organic substance-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for treating water excellent in light utilization, photocatalytic and gas utilization efficiencies, and also without requiring ozone treatment facilities when water is treated using a photocatalyst, and a method for treating water. <P>SOLUTION: In the apparatus for bringing organic substance-containing water into contact with the photocatalyst to treat it, the organic substance-containing water is decomposed to be removed by a photocatalytic reaction under presence of an oxygen-containing gas having a bubble diameter of 0.1 to 50 μm using the photocatalyst such as titanium oxide, light irradiation means such as a high-pressure mercury-vapor lamp for irradiating the photocatalyst with light and a fine bubble supply means for supplying a fine bubble of the oxygen containing gas having a bubble diameter of less than 100 μm to the organic substance-containing water. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic substance-containing water treatment apparatus that oxidizes organic substance-containing water with a photocatalyst and a method for treating organic substance-containing water.

  Water treatment technology using an accelerated oxidation method that decomposes organic substances in water using OH radicals with strong oxidizing power generated by combining ultraviolet rays, ozone, hydrogen peroxide, etc. is applied to various wastewaters Has been.

  Ozone has the disadvantages of low dissolution efficiency in water and a short half-life in water. Furthermore, since ozone is harmful to the human body, facilities for airtight treatment and waste ozone treatment must be provided, and the running cost becomes very high.

  Moreover, in the accelerated oxidation method using hydrogen peroxide and ultraviolet rays in combination, it is difficult to keep the reaction conditions constant because hydrogen peroxide acts on both the oxidizing agent and the reducing agent depending on the oxidation-reduction potential of the water to be treated. Yes, decomposition efficiency is very low.

Therefore, as a technique for solving these disadvantages, a technique for treating organic substance-containing water using a photocatalyst has been proposed. For example, Patent Document 1 discloses that water to be treated in which submicron titanium oxide particles are mixed is stirred by supplying compressed air in a tank to decompose organic substances. Patent Document 2 discloses that an organic substance is decomposed by a photocatalyst while supplying dissolved oxygen into the organic substance-containing water through an oxygen-permeable diaphragm. Furthermore, Patent Document 3 describes that organic substance-containing water is treated with a photocatalyst while supplying fine ozone bubbles to the organic substance-containing water.
JP 2001-070935 A JP 2004-066099 A JP 2004-267974 A

  However, even in the methods described in Patent Document 1 and Patent Document 2, the processing efficiency of the photocatalyst itself cannot be said to be sufficient. For this reason, the number of lamps and the amount of catalyst increase, and the running cost increases. There has been a demand for further improvement in processing efficiency. Moreover, in the invention described in Patent Document 3, although the decomposition efficiency of organic matter is excellent, the same problem as the treatment using ozone, that is, the problem that equipment for airtight treatment and waste ozone treatment must be provided Had.

  The organic substance-containing water treatment apparatus according to claim 1 is an apparatus for treating organic substance-containing water by contacting it with a photocatalyst, a photocatalyst, a light irradiation means for irradiating the photocatalyst with light, and a fine oxygen-containing gas in the organic substance-containing water. And a fine bubble supply means for supplying bubbles.

  The organic matter-containing water treatment apparatus according to claim 2 is characterized in that, in claim 1, the fine bubbles generated by the fine bubble supply means are 100 μm or less.

  The organic substance-containing water treatment apparatus according to claim 3 is characterized in that, in any one of claims 1 and 2, the oxygen-containing gas is treated by means for increasing the oxygen concentration.

  The method for treating organic substance-containing water according to claim 4 includes a step of supplying oxygen-containing gas fine bubbles to the organic substance-containing water, contacting the organic substance-containing water supplied with the oxygen-containing gas fine bubbles with a photocatalyst and irradiating light. And a step of performing.

  The present invention is excellent in light utilization efficiency, photocatalytic efficiency, and gas utilization efficiency when water treatment is performed using an oxidation action by a photocatalyst.

  Hereinafter, preferred embodiments of the present invention will be described in detail. In addition, embodiment described below shows the example of the water treatment apparatus and water treatment method concerning this invention, and this invention is not limited narrowly by these illustrated embodiment.

  FIG. 1 is a diagram schematically showing a configuration of a preferred embodiment of an organic matter-containing water treatment apparatus of the present invention. The organic matter-containing water 1 is temporarily stored in the storage tank 2. Here, the organic substance-containing water 1 includes a wide range of sewage, drainage, waste water, industrial water, water for producing pure water, and the like that require oxidative decomposition of the organic substance, and is not particularly limited.

  The organic substance-containing water 1 temporarily stored in the storage tank 2 is fed to the reaction tank 7 after the fine bubbles of oxygen-containing gas are supplied by the fine bubble supply means 5 by the pump 3. Here, the fine bubble supply means 5 is not particularly limited, but any fine bubble supply means can be used as long as it can generate bubbles having a bubble diameter of 100 μm or less, preferably 50 μm or less. . For example, a device in which a pressure pump and an ejector are combined, or a device using a spherical body described in Japanese Patent Application Laid-Open No. 2003-305494 may be used. As the fine bubble supply means combining the pressurizing pump and the ejector, there is an apparatus that diverts a part of the organic substance-containing water, sucks the oxygen-containing gas by the pressurizing pump and the ejector, and generates the fine bubbles in the pipe flow path. .

  The bubble diameter of the fine bubbles generated by the fine bubble supply means 5 is determined by determining the required oxygen dissolution rate according to the concentration of the substance to be removed of organic substance-containing water, and determining the bubble diameter according to the determined value, Specifically, it is more preferably 100 μm or less, particularly 0.1 to 50 μm. This is because the dissolution rate of oxygen is not sufficient when it is 100 μm or more, and a large amount of power is required to reduce the bubble diameter when it is 0.1 μm or less.

  In addition, as the oxygen-containing gas used in the present invention, air, oxygen, or the like can be used, but when air is used, it is represented by an oxygen-enriched film, PSA, or the like before being sent to the fine bubble supply means. It is preferable to have a gas treatment step for increasing the oxygen concentration by the oxygen separator.

  The organic substance-containing water 1 supplied with the fine bubbles of the oxygen-containing gas is supplied to the reaction tank 7, contacts the photocatalyst 6 filled in the reaction tank 7, and emits light from the light irradiation unit 8 provided in the reaction tank 7. , And the organic matter to be removed in the organic substance-containing water is oxidatively decomposed by the photocatalytic action of the photocatalyst 6.

  There is no restriction | limiting in particular in the photocatalyst used in this invention, What was fix | immobilized to the powder, the granular form, and the three-dimensional body may be used. In addition, the substance constituting the photocatalyst is not particularly limited, and examples thereof include metal oxides such as zinc oxide, tungsten oxide, titanium oxide, and cerium oxide, and metal oxides such as zinc sulfide, cadmium sulfide, and mercury sulfide. These metals may be doped with impurity ions such as nitrogen ions and sulfur ions, or those metals may be supported with a metal such as platinum.

  Among these, titanium oxide is also advantageously used in the present invention because of its structural stability, ability to remove harmful substances by photooxidation reduction reaction, safety in handling, and the like. Examples of the titanium oxide include general-purpose titanium dioxide, titanium oxide such as metatitanic acid, orthotitanic acid, hydrous titanium oxide, hydrated titanium oxide, titanium hydroxide, and titanium peroxide, and titanium hydroxide. Among them, anatase and titanium oxide having a rutile crystal structure are relatively inexpensive and have excellent performance. Furthermore, the efficiency in the photoreaction can be improved by supporting a metal such as platinum.

  In general, titanium oxide absorbs an ultraviolet light region of 380 nm or less and exhibits an effect. However, by doping with impurity ions such as nitrogen ions and sulfur ions, titanium oxide is a photocatalyst even in a visible light region of 380 nm or more and 650 nm or less. The light irradiation means other than the ultraviolet irradiation device can also be applied.

  However, as long as the titanium oxide in the present invention has a photocatalytic function, the crystal structure, crystallinity, etc. are not limited.

  In the present invention, the above-described photocatalyst itself or the carrier carrying the photocatalyst is used so as to form a fluidized bed or a fixed bed in the reaction tank 7. When used as a fixed bed, the light utilization efficiency can be improved by using a photocatalyst carried on a carrier such as Raschig ring made of a light transmissive material such as quartz glass.

  The light irradiation unit 8 used in the present invention can irradiate, for example, a hydrogen discharge tube, a xenon discharge tube, a mercury lamp, a laser light source, a light emitting diode (LED), etc., with which the photocatalyst used discards the photocatalytic function. A light source can be appropriately employed.

  In the present embodiment, the light irradiation unit 8 is provided inside the reaction tank 7, but may be provided outside the reaction tank 7, or may be provided both inside and outside the reaction tank 7.

  The treated water from which the organic matter has been decomposed and removed by the organic substance-containing water treatment apparatus as described above is taken out from the upper part of the reaction tank 7, temporarily stored in the adjacent treated water tank 10, and then used for a predetermined purpose. The liquid is sent to.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
Polyoxyethylene alkyl ether is dissolved in pure water to adjust 500 L of organic substance-containing water having a TOC (total organic carbon) concentration of 10 mg / L, and the organic substance-containing water is circulated using the apparatus shown in FIG. The TOC concentration of organic substance-containing water was measured over time. The circulating treatment was performed by returning the treated water taken out from the reaction tank 7 to the storage tank 2 without sending it to the treated water tank 10. The photocatalyst uses 1.5 kg of Degussa titanium oxide P-25 (average particle size 0.021 mm), the light source uses a high-pressure mercury lamp with a main wavelength of 365 nm, and air as the oxygen-containing gas has a bubble diameter of 5 It was added at 10 μm and a feeding rate of 30 L / min. The results are shown in Table 1.
Example 2
As long as oxygen was used instead of air, the organic material-containing water was treated under the same conditions as in Example 1. Table 1 shows changes with time in the TOC concentration of organic substance-containing water.
Comparative Example 1
The organic material-containing water was treated under the same conditions as in Example 1 except that ozone gas was used instead of air. Table 1 shows changes with time in the TOC concentration of organic substance-containing water.
Comparative Example 2
The organic material-containing water was treated under the same conditions as in Example 2 except that a normal air diffuser was used instead of the fine bubble supply means. In addition, the bubble diameter of the bubble generate | occur | produced with a diffuser tube was 1-5 mm. Table 1 shows changes with time in the TOC concentration of organic substance-containing water.

  As is apparent from the results shown in Table 1, when a normal air diffuser was used (Comparative Example 2), even when oxygen gas was used, sufficient TOC removal efficiency was not exhibited. When the oxygen-containing gas is supplied by the fine bubble supply means, the effect of removing the TOC that greatly squeezes Comparative Example 1 even when air is used (Example 1), and when oxygen gas is used (Example) 2), the TOC removal effect was almost the same as when ozone gas was used (Comparative Example 1).

  INDUSTRIAL APPLICABILITY The present invention can be used as a water treatment apparatus or method for performing organic matter decomposition treatment of various sewage, wastewater, wastewater, or removal of organic matter in the production process of pure water or water.

It is explanatory drawing of the one aspect | mode of this invention apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic substance containing water 2 Storage tank 3 Liquid feed pump 4 Oxygen containing gas 5 Fine bubble supply means 6 Photocatalyst 7 Reaction tank 8 Light irradiation part 9 Treated water 10 Treated water tank

Claims (4)

An apparatus for treating organic substance-containing water in contact with a photocatalyst,
An organic substance-containing water treatment apparatus comprising: a photocatalyst; a light irradiation means for irradiating light to the photocatalyst; and a fine bubble supply means for supplying fine bubbles of an oxygen-containing gas to the organic substance-containing water. In claim 1,
An organic substance-containing water treatment apparatus, wherein fine bubbles generated by the fine bubble supply means are 100 μm or less. In either claim 1 or 2,
An organic substance-containing water treatment apparatus, wherein the oxygen-containing gas is treated by means for increasing the oxygen concentration. Supplying fine bubbles of oxygen-containing gas to organic substance-containing water;
Contacting the photocatalyst with organic substance-containing water supplied with fine bubbles of oxygen-containing gas and irradiating light; and
A method for treating water containing organic matter, comprising:

Images