JP2002346577A - Wastewater treatment method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wastewater treatment method solving such a problem that there is a limit in the miniaturization of a wastewater treatment apparatus because a treatment process is required at every component to be treated in conventional wastewater treatment to make it possible to treat hardly decomposable organic components and fine particle components at the same time, and an apparatus therefor. SOLUTION: A ceramic filter film containing photocatalyst particles in a dispersed state is immersed in wastewater to be treated and wastewater is sucked and filtered through a filter film and the surface of the filter film is irradiated with ultraviolet rays to generate an oxidation-reduction reaction. Further, oxidizing gas is sent into the wastewater from a region under the filter film not only to remove refuse adhering to the surface of the filter film but also to oxidize and decompose components in the wastewater. Fine particle components and organic components in wastewater can be removed by filtration due to the filter film, decomposition curing due to the photocatalyst and oxidative decomposition effect due to the oxidizing gas. The wastewater treatment apparatus is also disclosed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for removing wastewater generated from various situations, such as a washing process, a polishing process, a washing process in a general household, a washing of dishes, and a waste treatment in a company. The present invention relates to a wastewater treatment method for removing impurities in water and an apparatus therefor.

[0002]

2. Description of the Related Art In general, the place where the largest amount of wastewater is generated is a production factory.
Wastewater treatment is usually carried out according to each law and local situation. The purpose of wastewater treatment is to remove impurities in water. For example, impurities such as SS components (suspended substances), ionic components such as silica, and dissolved components of organic solvents and surfactants are typical removal targets. is there. The wastewater treatment process allows the treated water to be reused in the process again, or to be discharged below a discharge standard.

[0003] Taking a typical wastewater treatment process as an example, wastewater treatment consists of a number of processes.
Each step is provided for treating a different substance to be removed. The wastewater treatment process will be described below by taking wastewater treatment generated from the glass lens washing process as an example. The glass lens washing process is roughly divided into washing, rinsing, and drying processes. Among them, water discharged from the rinsing process is an object to be treated as wastewater. Rinse wastewater contains detergent components such as surfactants and builders brought in from the washing tank, and components that are attached to the glass lens due to pre-cleaning processing such as abrasives, cutting chips, and cutting oil residues. It is included as a processing target. The general treatment process for wastewater containing these components is removal of ionic components by ion exchange resin, adsorption and removal of organic components by activated carbon, biological filtration by activated sludge, microfiltration membrane, reverse osmosis membrane and ultrafiltration membrane. A method is used in which filtration or the like is used in combination as necessary. By these steps, impurities are effectively removed from the wastewater.

However, in such a conventional wastewater treatment method, since a different treatment step is required for each substance to be removed, the entire treatment step is very long, and the wastewater treatment apparatus is accordingly enlarged. There are drawbacks. For example, considering the above-described glass washing process, processes such as microfiltration, ion exchange, ultrafiltration, and removal of dissolved matter by activated carbon are indispensable, and there is a limit to shortening the process and miniaturizing the apparatus. However, from the viewpoint of production cost, production stability, equipment maintenance, and the like, it is desirable that the number of wastewater treatment steps be as small as possible.

[0005] Furthermore, in recent years, with increasing public awareness of environmental conservation, it has become necessary to manage wastewater treatment with stricter standards. Particularly, wastewater containing an aromatic organic compound or a chlorine-based compound requires strict control, especially to a very low concentration, due to its characteristics. However, these substances are generally hardly decomposable, and it is not easy to carry out treatment to a low concentration in a simple process. Therefore, in order to treat wastewater containing hardly decomposable substances, in addition to the general methods described above, methods such as heat treatment and chemical treatment are often employed. In addition, there are problems such as an increase in the amount of waste and an increase in the number of processes.

[0006]

As a technique for decomposing such hard-to-decompose terrestrial substances, a water treatment method using a photocatalyst has attracted attention in recent years. The photocatalyst is a technique for decomposing an organic substance by an oxidation-reduction reaction on a surface by using characteristics of an optical semiconductor. Degradation using photocatalysts has the advantages of low running costs due to the use of catalytic reactions, high safety because no special chemicals are used, and a wide variety of decomposable substances. The features are generally mentioned, and accordingly, various uses utilizing photocatalysts have been proposed.

However, in the photocatalytic decomposition technique, in order to obtain high decomposition efficiency, it is necessary to increase the irradiation amount of the photocatalyst and increase the contact between the waste liquid and the photocatalyst. In order to satisfy these requirements, when a wastewater treatment using a photocatalyst is implemented in a device, a method using a powdery photocatalyst is often used. This is a method in which a photocatalyst having a diameter of about 1 mm or less is put into wastewater and dispersed by a stirrer or the like, thereby improving the above-mentioned required amount of light irradiation and the amount of contact with the liquid, thereby increasing the decomposition efficiency. This method is already known, for example, from JP-A-9-85295.

However, a disadvantage of this method is that it is not easy to recover the dispersed photocatalyst. In order to obtain a high decomposition effect, it is desirable that the photocatalyst be small and widely dispersed uniformly. However, the smaller the particle size of the photocatalyst becomes, the more difficult it is to recover the photocatalyst. For example, when the photocatalyst is recovered by a film, the frequency of clogging of the film necessarily increases. Backwashing of the membrane may be performed to remove the powder adhering to the membrane, but even in this case, the frequency of clogging does not decrease, and time loss and deterioration of the membrane due to backwashing are inevitable. .

[0009]

According to the present invention, there is provided:
A ceramic filtration membrane containing a photocatalyst substance in a uniformly dispersed state is immersed in a liquid, and the submerged membrane is irradiated with light to decompose organic substances in the liquid by a photocatalyst. An object of the present invention is to provide a wastewater treatment method and apparatus for removing components.

According to the present invention, a photocatalytic effect and a membrane filtration effect can be obtained simultaneously, and an oxidizing gas is blown out from a portion directly below the membrane at the lower part of the apparatus, and the oxidizing gas is brought into contact with the membrane to thereby attach fine particles to the membrane surface. In addition, wastewater treatment is achieved which has the effect of preventing organic substances in wastewater from being oxidized and decomposed by oxidizing gas.

Hereinafter, the effect of the present invention will be specifically described with reference to FIG. 1 as an example, but the present invention is not limited to this.

FIG. 1 schematically shows an example of a wastewater treatment apparatus for carrying out the present invention. In the wastewater treatment according to the present invention, wastewater treatment is performed by the submerged filtration membrane 1. This submerged film contains the photocatalyst 2 and is installed inside the processing tank 4 together with the gas outlet 3. The submerged film is made of a ceramic sintered body,
The filtration diameter is not particularly limited, but is generally 100 μm or less. The photocatalyst may be a generally known photocatalyst material such as titanium oxide, tungsten oxide, and zirconium oxide. Titanium oxide is particularly desirable in terms of the semiconductor band width, conduction band position, and the like. The photocatalyst is exposed on the surface of the filtration membrane and is contained in a state protruding from the surface of the membrane. Organic matter is decomposed by the photocatalyst protruding from the surface, but since the photocatalyst protrudes from the membrane, the area in contact with wastewater is large, and decomposition can be performed with high efficiency. The shape of the photocatalyst itself is not particularly limited, but it is necessary that the presence of the photocatalyst does not hinder the function of the filtration membrane. The gas outlet is provided immediately below the submerged film, and the oxidizing gas sent from the gas supply pump 5 is blown out from the outlet. The outlet is located at the position where the oxidizing gas comes into contact with the surface of the filtration membrane, so that it prevents clogging of the membrane surface due to contact with the oxidizing gas and has the effect of decomposing organic substances near the membrane surface. .

The wastewater treatment is sucked out of the tank by the circulation pump 6 through the submerged membrane in the treatment tank and transferred to the next step by the transfer pipe 7. The organic matter concentration of the processing liquid is measured by a TOC meter 8 connected to the processing tank. The liquid in the tank is stirred by the stirring device 9, and the liquid in the tank is maintained in a uniform state. This stirrer may be a general stirrer rotating. Further, an ultraviolet lamp 10 is provided inside the tank. The ultraviolet lamp irradiates the photocatalyst with ultraviolet rays, thereby causing an oxidative decomposition reaction on the surface of the photocatalyst. Since the ultraviolet lamp does not come into direct contact with the processing liquid, it is usually installed in the liquid in a state of being placed in a quartz tube having a high ultraviolet transmittance. The UV lamp may be a low-pressure lamp or a high-pressure lamp, but the larger the output, the greater the decomposition effect. Therefore, a high-power lamp is preferable in order to obtain high decomposition efficiency, but in that case, the temperature of the air or liquid near the ultraviolet ray rises, and if temperature control is necessary, measures must be taken. .

The treatment liquid is treated as described above and transferred to the next step, and at the same time, new wastewater is fed into the treatment tank through the transfer pipe 11 from the previous step.

As is clear from the above description,
In the present invention, a photocatalyst is contained in a dispersed state in a liquid immersion film, and the film is irradiated with ultraviolet rays and brought into contact with a gas having an oxidizing effect, whereby wastewater is combined with a combined effect of a photocatalytic effect, a filtering effect, and an oxidizing effect. It is an object of the present invention to provide a wastewater treatment method for performing treatment and a device therefor.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The effects of the present invention will be described with reference to the following embodiments, but the present invention is not limited to these embodiments.

Water treatment is carried out using the apparatus shown in FIG. The tank capacity is 150 l and the average particle size in water is 0.5 m
A ceramic filtration membrane containing 100 g of m ₂ titanium oxide (chemical formula TiO ₂ ) is installed. The filtration membrane is 200 mm long, 200 mm wide, 10 mm thick, and has a filtration diameter of 1 mm.
Three pieces having a thickness of 0 μm were placed in parallel near the center of the tank at an interval of 20 mm. The filtration membrane is connected to a suction pump. In this embodiment, in order to measure the change in water quality, the water in the tank is filtered by the suction pump at a rate of 100 ml / min and then circulated again into the tank. The structure is

A gas outlet is provided at a distance of 100 mm below the filter membrane. The gas outlet is composed of 20 holes having a diameter of 2 mm, and air is blown from the outlet at a rate of 1000 ml per minute. The blown air floats while contacting the surface of the filtration membrane. Further, an ultraviolet lamp is installed in the tank, and a high-pressure mercury lamp manufactured by Ushio Inc. 100 W is used as this lamp.

Using this apparatus, an organic substance concentration of 40 pp
m and 60 ppm of water, and the total organic carbon concentration (T
The results obtained by measuring the OC concentration) are shown in Examples 1 and 2.
As shown in Table 1.

The results obtained when the same treatment as in Examples 1 and 2 was performed except that a filtration membrane containing no titanium oxide was used are shown in Table 1 as Comparative Examples 1 and 2. Table 1 shows the results of Comparative Example 3 and Comparative Example 4 in the case where the same processing as in Example 1 and Example 2 was performed except that no ultraviolet lamp was irradiated. TOC was measured using a TOC analyzer model 810 manufactured by SIEVERS.

[0021]

[Table 1]

It can be seen from the examples that the effect of the present invention is clear.

[0023]

According to the present invention, the following effects can be obtained. 1. In wastewater treatment, the processing of suspended solids and dissolved organic substances, which previously required separate treatment steps, can be treated as one step in one treatment tank, thus shortening the steps and reducing the installation space. Becomes possible. 2. Organic substances can be treated with higher efficiency than conventional methods of treating organic substances such as activated carbon treatment and biological treatment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a wastewater treatment device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filtration membrane in liquid 2 Photocatalyst 3 Oxidizing gas blow-out port 4 Reaction tank 5 Gas supply pump 6 Circulation pump 7 Liquid transfer pipe to next process 8 TOC meter 9 Stirrer 10 Ultraviolet lamp 11 Liquid transfer pipe from previous process

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taishi Saeki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Otsuka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F term in the company (reference) 4D019 AA03 BA05 BB01 BC07 CA05 4D037 AA11 AB01 BA18 CA02 CA12 4D050 AA13 AA15 AB11 BB01 BB02 BC06 BC09 BD06 CA15

Claims (3)

[Claims] In a wastewater treatment step, wastewater having a structure in which a ceramic filtration membrane into which photocatalyst particles are mixed in a dispersed state, and an ultraviolet lamp for irradiating ultraviolet rays to the filtration membrane is installed in a wastewater treatment tank. A wastewater treatment method and a wastewater treatment method, wherein wastewater treatment is performed by suction filtration and decomposition reaction using a photocatalyst using a treatment device. 2. The wastewater treatment apparatus according to claim 1, further comprising a gas outlet at a lower portion of the filtration membrane in the wastewater treatment tank, wherein an oxidizing gas discharged from the gas outlet contacts the filtration membrane. Characterized wastewater treatment method and apparatus. 3. A wastewater treatment method and apparatus according to claim 1, wherein the oxidizing gas is oxygen, air, or ozone.