JPS6127118B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ozone reaction type wastewater treatment device that treats pollutants in wastewater by injecting ozone into the wastewater.

[Technical background of the invention and its problems]

Ozone, which has strong oxidizing power, has recently begun to be used in various wastewater treatments to prevent pollution. The use of ozone in wastewater treatment is particularly suitable for the oxidative decomposition of pollutants that are difficult to treat with conventional biological treatment, or pollutants that are toxic to living organisms, such as cyanide compounds and phenolic compounds. .

In recent years, due to the increase in water demand, an increasing number of companies are not only treating and discharging wastewater, but also reusing wastewater by performing advanced treatment that combines physical, biological, and chemical treatments. Furthermore, with the development of urban sewage systems, the amount of secondary treated sewage discharged from treatment plants is increasing, and conventional sedimentation and biological treatment alone are insufficient for purification, resulting in increased pollution of rivers and the sea after discharge. are doing. Therefore, from the standpoint of environmental conservation, more advanced sewage treatment is required.
Due to this increase in demand for water, research and development efforts are being carried out in various places to provide advanced treatment to this large amount of secondary treated sewage water and to purify it to the point where it can be used as industrial water. The oxidizing power of ozone is used for advanced treatment of these industrial wastewater or secondary treated sewage water. Ozone is effective in deodorizing, decolorizing, sterilizing, and decomposing other organic contaminants, and is particularly effective in inactivating viruses. After ozone is added, excess ozone self-decomposes into oxygen, so there are no problems such as residual treatment chemicals or increased salt concentration, unlike in conventional chlorine treatment.
Furthermore, ozone has the advantage that it can be easily generated using electricity alone using air or oxygen as a raw material.

However, ozone is a gas at room temperature, and the ozone concentration obtained from an ozone generator is 1% (by weight) when air is used as the raw material, and about 2% when oxygen is used as the raw material.
% concentration can be obtained. For this reason, a gas-liquid contacting device is required to treat wastewater using ozone, and generally a porous dehydrator, a suction type injector, etc. are used to increase the gas-liquid contact area and introduce ozone into the wastewater. Injecting air or oxygen. The industrial wastewater that needs to be treated includes wastewater that contains a lot of surfactants such as water-soluble cutting oil and fluorescent flaw detection liquid, and the dyeing industry wastewater contains not only dyes but also many water-soluble polymer substances and detergents as adhesives and detergents. Contains surfactants. Furthermore, in factory wastewater intended for reuse, detergent often flows into the wastewater from cafeterias. On the other hand, at sewage treatment plants, substances that are difficult to treat using the activated sludge method, such as detergents from domestic wastewater and protein components from human waste, remain in the secondary treated sewage water. Wastewater containing these substances has a strong foaming property and becomes a hindrance to various wastewater treatment operations. Ozone's strong oxidizing power oxidizes and decomposes these foaming components.
It can be reduced in molecular weight and defoamed.

Conventionally, wastewater treatment equipment using ozone injects ozone-containing gas as fine bubbles from the bottom of the reaction tank in order to increase the gas-liquid contact time, water pressure, and bubble contact area, and promote the solubility and reactivity of ozone. .
Furthermore, unreacted ozone discharged from the upper part of the reaction tank is completely decomposed using activated carbon or a catalyst in the ozone decomposition tank to prevent air pollution.

However, when treating wastewater containing a large amount of foaming components, steady operation becomes difficult as described below. In other words, at the initial stage of operation, the foaming component in the reaction tank is present at a uniform concentration. When ozone-containing gas is injected, most of the ozone is consumed in the lower part of the reactor, and the ozone concentration in the rising bubbles becomes very low. Therefore, in the upper part of the reaction tank, the phenomenon is the same as that of bubbling simply due to gas injection. This also applies if there are substances in the wastewater that are more likely to react with ozone than foaming components. Bubbles generated in an area exceeding the space volume at the top of the reaction tank wets the activated carbon or catalyst layer in the ozone decomposition tank, which is installed to decompose exhaust ozone emitted from the ozone reaction structure, increasing pressure resistance and further decomposing exhaust ozone. reduce the effective surface area required for For this reason, even during regular operations after the foaming component has been oxidized with ozone, complete exhaust ozone decomposition becomes difficult. This problem caused by foaming occurs even in continuous processing.
This can occur due to changes in water quality.

Conventionally, pouring water into the generated foam to eliminate the foam has been carried out in general wastewater treatment. However, this method only destroys the foam, but does not essentially decompose and remove the foaming components. A method of defoaming foam by spraying an ozone-containing substance onto the foam is also known, but in this case, most of the ozone is released from the upper part of the ozone reaction tank as waste ozone, which is not economical.

[Purpose of the invention]

The purpose of the present invention is to suppress foaming by effectively injecting ozone into the foam generated at the initial stage of the operation when ozonating wastewater containing a large amount of foaming components.
It is an object of the present invention to provide an improved wastewater treatment device that can thereby prevent bubbles from moving into the ozone decomposition tank and continue stable treatment operations.

[Summary of the invention]

The wastewater treatment apparatus according to the present invention includes a tank in which wastewater is stored, a first day user installed in the lower part of the tank and configured to introduce ozone into the wastewater as bubbles, and a first dehydrator installed in the tank to create ozone bubbles in the wastewater. and a second dehyde user having a pore diameter larger than that of the first dehyde user,
Foaming is mainly suppressed by ozone bubbles generated from the second dehydrator.

[Embodiments of the invention]

The present invention will be described in detail below with reference to an embodiment shown in the drawings. In FIG. 1, 1 is an ozone reaction tank that injects ozone into wastewater to treat pollutants in the wastewater. The wastewater to be treated is introduced into the ozone reaction tank 1 through the inlet pipe 2, and the treated wastewater is discharged through the discharge pipe 8. Ozone generator 1
Ozone generated at 0 is passed through ozone introduction pipe 4 and valve 1
5 into a first dehydrator 5 made of a porous material provided at the bottom of the ozone reaction tank 1,
It is injected into the wastewater from this first day user 5. Ozone remaining without reacting in the ozone reaction tank 1 is sent to the ozone decomposition tank 11 through the exhaust ozone pipe 3, where the ozone is decomposed into harmless oxygen gas and released into the atmosphere. As mentioned above, the ozone decomposition tank 11 is composed of activated carbon, catalyst, etc., but when water adheres to its surface, the active area decreases. As a result, the ozone decomposition ability decreases, and in some cases, ozone may be released into the atmosphere without being decomposed, causing pollution.

Reference numeral 16 denotes a second dehydrator user provided especially for defoaming in the present invention, to which ozone is supplied through a branch pipe 9 branched from the ozone introduction pipe 4 and a valve 7. The second dehyde user 16 is provided near the first dehyde user 5 in the ozone reaction tank 1, and has a larger pore size for generating air bubbles than the first dehyde user 5.

In the above configuration, at the beginning of wastewater treatment, the valve 15 is first closed, the valve 7 is opened, and the second day user 16 is opened.
supply ozone to Since the pore diameter of the second dehyde user 16 is larger than that of the first dehyde user 5, the diameter of the generated ozone bubbles becomes larger, and the solubility of ozone decreases. For this reason, Dehy user 16
The ozone supplied by the reactor reacts less in the lower part of the reaction tank 1, and the ozone concentration rises to near the water surface without decreasing, so it effectively acts on the bubbles near the water surface.
It can defoam efficiently. When defoaming progresses, valve 7 is closed and valve 15 is opened to supply ozone to the first dehydrator user. Since the pore diameter of the first day user 5 is small, the diameter of the ozone bubbles is also small.
Since the solubility is increased, it is effectively dissolved in the ozone reaction tank and ozone treatment is performed efficiently.

Here, the relationship between the pore diameters of the first day user 5 and the second day user 16 will be described. In general, the relationship between the pore size of the dehyde user and the ozone dissolution rate differs depending on various conditions, but in the case of raw tap water, at a depth of 5 m or less, the pore size of the dehyde user is approximately 80% in the range of 30 μm to 60 μm. Maintain high ozone absorption rate. On the other hand, when the pore size exceeds 90 μm, the ozone absorption rate decreases significantly.
3 to 100 μm to 1 mm bubbles from the dehydrator
5 mm (water depth of 3 to 4 m), and it is known that if a dehydrator with a diameter of 100 μm or more is used, the absorption efficiency will be 60% or less. A similar absorption characteristic occurs for wastewater in the present invention, and if the pore diameter of the second dehydrator 16 is set using the above pore diameter as a guide, a relatively high ozone concentration can be maintained up to the liquid level, and bubbles can be suppressed at the liquid level. A breaking effect occurs.

Figure 2 shows the case when the second day user 16 is used.
FIG. 3 is a diagram showing the bubble generation situation in (A) and when not used (B). That is, in the case of (B), the height h of the bubbles becomes higher than the height _h0 of the space above the water surface of the ozone reaction tank 1, and the bubbles move to the ozone decomposition tank 11, and in the case of (A), this can be prevented. It shows.

〔Effect of the invention〕

As explained above, according to the present invention, in an ozone reaction type wastewater treatment apparatus that injects ozone into wastewater to treat pollutants in the wastewater, in addition to the first dehydrator that injects reactive ozone, To break up the bubbles near the water surface that are often present at the beginning of the operation,
By providing a second dehydrator with a large pore size for generating bubbles, it is possible to effectively eliminate bubbles, thereby preventing the bubbles from increasing and migrating into the ozone decomposition tank and reducing the ozone decomposition ability. It can be prevented. Therefore, it is possible to obtain a rational wastewater treatment device that can continue to operate safely without emitting residual ozone into the atmosphere.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the wastewater treatment apparatus according to the present invention, and FIG. 2 is a characteristic diagram showing the defoaming effect according to the present invention. DESCRIPTION OF SYMBOLS 1... Ozone reaction tank, 5... Main first dehydrator user, 16... Second dehyde user, 10... Ozone generator, 11... Ozone decomposition tank.

Claims (1)

[Claims] 1. A tank in which wastewater is stored, and first and second day users that are provided close to each other in the lower part of this tank and send ozone into the waste water as bubbles, and the pore diameter of the first day user is , the size is set to produce bubbles with a high rate of ozone dissolution into the wastewater in the tank, and the pore size of the second dayhy user is larger than the pore size of the first daytime user, and the rate of ozone dissolution into the wastewater in the tank is set. A wastewater treatment device characterized in that the size of the bubbles is set such that bubbles are reduced by 20% or more.