JPH1110142A - Waste water treatment process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decolor simply waste water and discharge the same as environmental water free from the pollution feeling by carrying out the oxidization reaction treatment of colored waste water containing a dye with the reaction of a photocatalyst. SOLUTION: In the case of treating colored waste water containing a dye of large coloring strength discharged out of a coloring plant or a dye synthesizing plant, a photocatalyst is used, and also the water is treated by the photocatalyst and then treated biologically or reverse osmosis treated to recycle the water for use. As for the photocatalyst, titanium oxide, strontium titanate or the like is preferred from the viewpoints of conditions of catalyst activities, safety, price and the like, and the photocatalyst is used alone in the powdery shape, granular shape or the like and dispersed in water, or used in the state of being carried on carriers of various shapes such as the membrane shape, porous shape, fiber shape or fabric shape. As a light source emitted for the purpose of energizing the photocatalyst, a source including the wavelength of generating the electric charge separation of the photocatalyst, for example, a filament lamp, a mercury lamp or the like is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment, and more particularly, to an efficient treatment by treating a wastewater with a photocatalyst before biological treatment, or a wastewater reacted with a photocatalyst. The present invention relates to a wastewater treatment method in which water can be recycled by treating with a reverse osmosis membrane.

[0002]

2. Description of the Related Art Recently, the problem of pollution of environmental water by colored wastewater has been greatly increased. In particular, wastewater from dyeing factories and dye synthesis factories has a high coloring strength, so that it tends to give a feeling of contamination, and measures to prevent it have been required. The number of dyeing factories is extremely large and is distributed locally as a local industry. Generally, the composition of the effluent from these factories is very complex. There are many types of fiber materials, many types of dyes, auxiliaries, and chemicals are used for dyeing, the dyeing process is complicated, and the amount of water and the quality of water vary significantly. As a method for treating these wastewaters, a coagulation sedimentation method and an activated sludge method have been mainly used so far.

[0003]

However, the problems with these methods are that, in the coagulation sedimentation method, in addition to the inability to sufficiently remove the coloring components, the amount of coagulated sludge is large, resulting in an increase in waste. . Further, in the activated sludge method, since the dye component is a biologically hardly decomposable substance, there is a problem that it is hardly treated and coloration of environmental water is easily caused. The present invention has been made to solve the above problems, and a wastewater treatment method capable of easily decolorizing wastewater and discharging the wastewater as a pollution-free environment water or reusing it as recycled water. It is intended to make suggestions.

[0004]

In order to achieve the above object, the present invention basically has the following arrangement.

[0005] A wastewater treatment method in which dye-containing colored wastewater is oxidized by a photocatalytic reaction and treated, or a wastewater treatment method characterized by subjecting wastewater to an oxidative reaction by a photocatalytic reaction and then biologically treated. A wastewater treatment method characterized in that a reverse osmosis membrane treatment is performed after the oxidation reaction by the reaction, and water is recycled.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The wastewater used in the present invention can be divided into wastewater for dyeing fibers and wastewater from a plant for synthesizing dyes and intermediates thereof. Dye-containing dyeing wastewater in the dyeing of fibers, in addition to the wastewater from the dyeing process in general,
Since wastewater from processes such as desizing, scouring and bleaching as a pre-process, and finishing in a post-process is also included, various substances related to these processes are also included in addition to dyes. There are two types of dyeing processes: dip dyeing and printing. The former is a method of dyeing uniformly in a dye bath in which dyes and auxiliaries are dissolved. The latter is a method in which paste containing dyes is transferred to cloth using a mold. ,
In this method, the dye is fixed and dyed by post-treatment. Therefore, there are some differences in the composition of the same dyeing process wastewater. In the dip dyeing method, depending on the type of fiber to be dyed, direct dye, acid dye, basic dye, mordant dye,
Various dyes such as disperse dyes, vat dyes, reactive dyes and sulfur dyes are used.
Salts such as sodium sulfide, sodium sulfate and sodium carbonate as dispersants, accelerators and leveling agents, acids such as sulfuric acid and acetic acid, and anionic and nonionic surfactants; mordanting agents such as tannin and potassium bichromate; Ferric chloride is used as an agent, and a polymer base is used as a dye fixing agent. In the printing method, in addition to the various dyes described above,
In addition to the use of fluorescent pigments and general pigments, rubber and natural or processed or synthetic pastes and pigments are used as pastes, so polymers and petroleum are used to attach them to fibers and adjust printing paste. An emulsion of a system solvent (a binder and an extender) is used. Desizing and scouring processes discharge surfactants, fiber scraps, and deposits on fibers, as well as paste, and the bleaching and finishing processes produce a small amount of microorganisms such as oxidizing agents. Is highly toxic to In addition to the fact that such dye-containing colored wastewater has a very complicated composition, there are many small and medium-sized factories as discharge sources, and the types of dyes and various auxiliaries vary depending on the fiber to be dyed. Fluctuations in water quality and quantity between days, months and seasons are very large. As an example of a colored drainage containing an infiltration dye, the drainage amount is 400 m ³ / day, COD is 300 to 500 mg / day.
L, coloring degree 500-2000 (dye concentration several tens to 100 mg /
L order).

On the other hand, the dye-containing colored wastewater from the dye and its intermediates also contains a large amount of various organic compounds in addition to the dye, and most of them are chemically synthesized products, so that microbial decomposition is difficult. There are many. Most of these factories perform multi-product small-quantity production by a batch process, and the variety of products changes in a relatively short period of time. To give an example of wastewater from a dye synthesis plant, the amount of wastewater is 200 to 300 m ³ / day, the degree of coloration is 50,000, COD is 25,000 mg / L, and both the degree of coloration and COD are extremely high.

Accordingly, the water quality characteristics of the dye-containing colored wastewater can be summarized as follows: the composition is very complicated,
H, BOD, COD, etc., water quality fluctuates greatly in a short period of time, high degree of coloring, contains a large amount of hardly decomposable substances such as dyes, and the like.

Examples of the photocatalyst in the present invention include metal oxides such as titanium dioxide, tungsten trioxide, zinc oxide, iron trioxide and strontium titanate; metal sulfides such as cadmium sulfide, zinc sulfide and indium sulfide; Metal selenides such as cadmium selenide and zinc selenide, metal phosphides such as germanium phosphide and indium phosphide, and metals and metal oxides such as platinum, rhodium, ruthenium, niobium, copper and iron for these photocatalysts And those conventionally known, such as those carrying. Among them, titanium dioxide, strontium titanate, and the like are particularly preferable in terms of catalytic activity, safety, and price.

The photocatalyst may be used by itself in a form in which powders, granules, etc. are dispersed in water, or in a state in which it is supported on carriers of various shapes such as membrane, porous, fibrous, and woven. Can be.

A major feature of this photocatalytic reaction is that it has a very strong oxidizing power. For example, when titanium oxide is used as a photocatalyst, it is known that holes that extract electrons from solution species under irradiation with near-ultraviolet light have a potential energy of 3.0 V (based on a standard hydrogen electrode potential). This is because of 1.23 V of O ₂ / H ₂ O, O ₃
Compared with 2.07 V of / O ₂ , it has a considerably high oxidizing ability, and can theoretically decompose almost all organic substances into water and carbon dioxide gas.

The light source for irradiating to excite the photocatalyst may be a wavelength (visible and / or visible) that causes charge separation of the photocatalyst.
Or ultraviolet). (For example, 387 nm or less for titanium dioxide). Specifically, an artificial light source such as a filament lamp such as an incandescent lamp, a high-intensity discharge lamp such as a mercury lamp or a xenon lamp, a fluorescent lamp, a black light, a germicidal lamp, a laser light, or a natural light source of sunlight is used. be able to. An artificial light source may be used at the same time as an auxiliary light source for the natural light source.

The biological treatment in the present invention refers to a process of decomposing by a microorganism, and can be divided into an aerobic bacteria treatment and an anaerobic bacteria treatment depending on the kind of bacteria. The activated sludge method is a representative of the aerobic bacteria treatment. Activated sludge treatment process means that floc-like biological multiplication body with purification function is constantly circulated in the biological reaction system as needed, and the ratio of substrate (BOD component of wastewater) and purification microorganisms is always in the aeration tank. Artificially manipulated to be constant, and in the presence of dissolved oxygen, the substrate and floc composed of microorganisms of different solid groups are brought into sufficient contact to aerobically oxidize and decompose this It is a processing process. Activated sludge is a mixed culture composed of microorganisms of different solid groups such as bacteria, fungi, protozoa and metazoans.

The reverse osmosis membrane of the present invention is a separation membrane that can be used for desalting low-concentration salt water (can water), desalinating seawater, and producing ultrapure water used for producing semiconductors. is there. Examples of the reverse osmosis membrane include an asymmetric cellulose acetate membrane (for example, US Pat. No. 3,133,132) and a linear aromatic polyamide membrane (for example, US Pat. No. 35,676).
No. 32) and a crosslinked aromatic polyamide film (for example, JP-B-63-36803). In this, as a reverse osmosis membrane, an ultra-thin film layer having substantially separation performance is coated on a microporous support membrane having substantially no separation performance, and the ultra-thin film layer is formed of a polyfunctional membrane. A crosslinked aromatic polyamide membrane obtained by interfacial polycondensation between an amine and a polyfunctional halide is preferred because of its high water permeability and high removal characteristics. Among the crosslinked aromatic polyamide films, a film whose surface is anion-charged is preferable because an organic substance of water obtained by oxidizing wastewater with a photocatalyst is anion-charged and thus has high removal characteristics.

The dye-containing colored wastewater is treated with a photocatalyst to decompose biologically hardly decomposable substances such as dyes and convert them into low-molecular-weight substances capable of decomposing organisms. It is possible to perform it. Also,
By decomposing the dye-containing colored wastewater with a photocatalyst, coloring substances such as dyes are decomposed and decolorized. In this treated water, since organic substances are decomposed into low molecular weight substances,
Even in the case where the reverse osmosis membrane is supplied and processed, the membrane surface fouling of the reverse osmosis membrane is extremely small, and it is possible to continuously and stably produce recycled water for a long period of time. In addition, since the photocatalyst-treated water contains a large amount of anion-charged substances, the use of an anion-charged membrane among the reverse osmosis membranes enhances the removal characteristics and makes it possible to produce clearer recycled water.

The ultrafiltration membrane used in the ultrafiltration membrane treatment or the microfiltration membrane treatment of the present invention includes an ultrafiltration membrane and a microfiltration membrane. The pore size of the filtration membrane is preferably smaller as the removal rate becomes higher, but is preferably 0.4 μm or less, more preferably about 0.1 μm, in view of the size of manganese oxide or iron oxide. The material of the filtration membrane is not particularly limited, and examples thereof include known polymer materials such as cellulose-based, polyamide-based, polysulfone-based, polyolefin-based, and polyacrylonitrile. The material can be appropriately selected depending on the required conditions at the time of use. For example, polyacrylonitrile can be selected if high strength is required, and polyolefin is used if hydrophobicity is desired.

As the ultrafiltration membrane or the microfiltration membrane, there are an internal pressure type for supplying raw water to the inside of the hollow fiber and an external pressure type for supplying raw water to the outside of the hollow fiber. The ultrafiltration membrane or microfiltration membrane, especially when there is an SS component in the wastewater, since the SS component is removed,
It is preferable to use the photocatalyst before the photocatalytic treatment because the photocatalytic efficiency is improved. However, the photocatalytic efficiency is not particularly limited, and the photocatalytic treatment may be used after the photocatalytic treatment or both before and after the photocatalytic treatment. Alternatively, the above-mentioned reverse osmosis membrane or biological treatment may be used in combination. For example, a combination with a front stage ultrafiltration membrane treatment, a middle stage photocatalytic treatment, and a subsequent stage reverse osmosis membrane treatment may be used.

[0018]

EXAMPLES Examples will be shown below, but the present invention is not limited to these examples.

(1) Method of Evaluating Absorbance In each experiment, the absorbance was measured using a UV-3100 self-recording spectrophotometer manufactured by Shimadzu Corporation. The decolorization rate D was calculated by the following equation.

D = (Ao-Ai) / Ao × 100 Ao: Absorbance before treatment Ai: Absorbance after treatment (Example 1) Sumfix Supr which is a reactive dye
a Br. Red 3BF (manufactured by Sumitomo Chemical Co., Ltd.) 7
0 ppm, sodium alginate 200 ppm and sodium bicarbonate
Aqueous solution obtained by mixing 150 ppm of sodium hydroxide, 30 ppm of sodium hexametaphosphate, 150 ppm of soda m-nitrobenzenesulfonate and 300 ppm of a nonionic surfactant.
000 cc was adjusted to make model dyeing wastewater. The BOD of the model dyeing wastewater was 38 ppm and the COD was 280 ppm. This aqueous solution was placed in a 1.5 L container equipped with a high-pressure mercury lamp (100 w), and 200 cm ² of a photocatalyst (manufactured by Nippon Inorganic Co., Ltd.) in which the surface of a glass fiber cloth with imitation woven fabric was fixed by a sol-gel method of titanium oxide was set. Then, an ultraviolet treatment was performed for 2 hours while stirring the aqueous solution. The BOD of the treated aqueous solution was 25 ppm and the COD was 150 ppm. The decolorization ratio of raw water and treated water was 85%. This treated water was permeated at a pressure of 10 kg / cm ² using a crosslinked aromatic polyamide reverse osmosis membrane SU-800 (manufactured by Toray Industries, Inc.). B of treated water obtained
The OD was 1 ppm or less, the COD was 1 ppm or less, and the decolorization rate was 99.9%. The surface of the reverse osmosis membrane after the treatment was hardly fouled.

(Comparative Example 1) The model dyeing wastewater used in Example 1 was directly subjected to a crosslinked aromatic polyamide reverse osmosis membrane SU-80.
0 (manufactured by Toray Industries, Inc.) at a pressure of 10 kg / cm ²
Through. The BOD of the obtained treated water is 2 ppm, C
The OD was 2 ppm, and the decolorization rate was 97%. Further, the surface of the reverse osmosis membrane after the treatment was stained red and was fouled.

Example 2 Sumifi, a reactive dye
x Supra Br. Red 3BF (manufactured by Sumitomo Chemical Co., Ltd.) 70 ppm and sodium alginate 200 ppm
And sodium bicarbonate (150 ppm), sodium hexametaphosphate (30 ppm) and m-nitrobenzenesulfonic acid soda (15).
1000 cc of an aqueous solution in which 0 ppm and 300 ppm of a nonionic surfactant were mixed was prepared to prepare a model dyeing wastewater. BOD of model dyeing wastewater is 38 ppm and COD is 2
It was 80 ppm. This aqueous solution is supplied with a high pressure mercury lamp (100
w), placed in a 1.5 L container with titanium oxide sol-gel method, and immobilized photocatalyst (manufactured by Nippon Inorganic Co., Ltd.) on the surface of a woven fabric having a woven pattern with a mosaic weave.
² was set, and an ultraviolet treatment was performed for 2 hours while stirring the aqueous solution. The BOD of the treated aqueous solution was 25 ppm and the COD was 150 ppm. This aqueous solution was subjected to biological treatment for 20 days using sludge of an urban sewage treatment plant in Shiga Prefecture. The resulting treated water was filtered through filter paper and analyzed.
The BOD was 5 ppm and the COD was 20 ppm. The decolorization rate was 90%.

(Comparative Example 2) Using the model dyeing wastewater used in Example 2, the sludge of an urban type sewage treatment plant in Shiga Prefecture was subjected to biological treatment for 20 days. The resulting treated water was filtered through a filter paper and analyzed. The BOD was 10 ppm and the COD was
Was 30 ppm. The decolorization rate was 70%.

Example 3 Sumifi, a reactive dye
x Supra Br. Red 3BF (manufactured by Sumitomo Chemical Co., Ltd.) 70 ppm and sodium alginate 200 ppm
And sodium bicarbonate (150 ppm), sodium hexametaphosphate (30 ppm) and m-nitrobenzenesulfonic acid soda (15).
1000 cc of an aqueous solution obtained by mixing 0 ppm and 300 ppm of a nonionic surfactant was added, and sewage drainage was further added.
MLSS was adjusted to about 10000 ppm to make model dyeing wastewater. BOD of model dyeing wastewater is 38 ppm COD
Was 280 ppm.

As the ultrafiltration membrane, a polyacrylic hollow fiber membrane having an average pore diameter of 0.01 μm and a membrane area of 12 m ² was used for external pressure filtration. The operation was stopped once an hour, and water was passed from the permeation side of the filtration membrane to the supply side for 20 seconds.
The hollow fiber membrane was oscillated by blowing air in minutes, and the filtration residue adhering to the surface was peeled off. 0.6 m ³ / hr of filtered water
The operation pressure was 0.35 (atm)
There was almost no pressure rise.

The filtrate from the ultrafiltration membrane is placed in a 1.5 L container equipped with a high-pressure mercury lamp (100 W), and a photocatalyst (Japan) is immobilized on the surface of a glass-fiber cloth with a woven pattern by the sol-gel method of titanium oxide. (Inorganic Co., Ltd.) 2
00 cm ² was set, and ultraviolet light treatment was performed for 2 hours while stirring the aqueous solution. BOD of treated aqueous solution is 25p
pm and COD was 150 ppm. The decolorization rate was 90%.

(Comparative Example 3) The same operation as in Example 3 was performed except that the treatment was not performed with the ultrafiltration membrane. The obtained treated water was filtered through a filter paper and analyzed. The BOD was 10 ppm and the COD was 30 ppm. The decolorization rate was 70%.

[0028]

According to the present invention, by utilizing the oxidative decomposition of the photocatalyst, the dye-containing colored wastewater can be easily decolorized and discharged as environmental water free of polluting, or reused as recycled water. A possible wastewater treatment method could be proposed.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 9/00 502 C02F 9/00 502G 502N 502R 503 503C 504 504B

Claims (6)

[Claims] 1. A wastewater treatment method for treating dye-containing colored wastewater with a photocatalyst. 2. A wastewater treatment method, wherein wastewater is treated with a photocatalyst and then biologically treated. 3. A wastewater treatment method comprising treating wastewater with a photocatalyst, treating the wastewater with a reverse osmosis membrane, and recycling and using the water. 4. The wastewater treatment method according to claim 2, wherein the wastewater is dye-containing colored wastewater. 5. The wastewater treatment method according to claim 1, wherein the photocatalyst is titanium dioxide. 6. The wastewater treatment method according to claim 1, wherein an ultrafiltration membrane treatment or a microfiltration membrane treatment is used in combination.