JPS5922597B2 - wastewater treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wastewater treatment device using ozone.

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 to purify the water, resulting in increased pollution of rivers and the sea after discharge. There is.

Therefore, from the standpoint of environmental conservation, more advanced sewage treatment is required.

Due to this increase in water demand, research and development efforts are being carried out in various places to highly treat this large amount of secondary treated sewage water and 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 only about 1% (by weight) when air is used as the raw material, and about 2% when oxygen is used as the raw material.

Therefore, to treat wastewater using ozone, a gas-liquid contacting device is required, and in general, a porous dihyuser, a suction-type injector, etc. are used to increase the gas-liquid contact area, and the air containing heozone in the wastewater is Or injecting 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 such 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 remain in the secondary treated sewage water, such as detergents from domestic wastewater and protein components from human waste.

Wastewater containing these substances has a strong foaming property and becomes a hindrance to various wastewater treatment operations.

Ozone's strong oxidizing power can oxidize and decompose these foaming components, converting them into low-molecular molecules and defoaming them.

Conventionally, wastewater treatment equipment using ozone has a short time of gas-liquid contact,
Ozone-containing gas is injected in the form of fine bubbles from the bottom of the reaction tank in order to increase the water pressure and bubble contact area and promote the melting 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 reactor wet the activated carbon or catalyst layer in the ozone decomposition tank, which is installed to decompose exhaust ozone emitted from the top of the ozone reactor, increasing the pressure resistance (and further increasing the exhaust ozone). Reduces the effective surface area required for ozonolysis.

For this reason, even during regular operations after the foaming components have been oxidized with ozone, complete exhaust ozone decomposition becomes difficult.

This problem caused by foaming can occur even in continuous treatment due to fluctuations 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.

The purpose of the present invention is to suppress foaming by effectively injecting ozone into the foam that is generated in the initial stage of the operation when wastewater containing a large amount of foaming components is ozonated. An object of the present invention is to provide an improved wastewater treatment device that can stably continue treatment operations by preventing the transition to wastewater.

The present invention will be described 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.

The ozone generated by the ozone generator 10 is transferred to the ozone introduction pipe 4
The gas is introduced into the first dihyuser 5 made of a porous material provided at the lower part of the ozone reaction tank 1, and is injected into the wastewater from the first dihyuser 5 as bubbles.

Ozone that remains unreacted 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.

This reduces the ozone decomposition ability, and in some cases, ozone may be released into the atmosphere without being decomposed, causing pollution.

Reference numeral 6 denotes a second dihydrator provided especially for defoaming in the present invention, and is installed near the surface of the wastewater.

Ozone is supplied to the second dihydrator 6 through a branch pipe 9 branched from the ozone introduction pipe 4 and a valve 7.

When the configuration shown in FIG. 1 is used, immediately after the start of wastewater treatment, there are many ozone reaction components in the wastewater, and as the ozone injected from the first main dihydrogen user 5 rises in the reaction tank 1, the ozone concentration rapidly increases. In particular, the foam that accumulates near the water surface cannot be defoamed.

However, since the ozone injected from the second dihyuser 6 immediately acts on the bubbles on the water surface, the bubbles are extinguished efficiently.

Therefore, the height of the bubbles is reduced, and the bubbles containing moisture do not pass through the exhaust ozone pipe 3 to the ozone decomposition tank 11 as in the conventional case, and the decomposition capacity in the ozone decomposition tank 1 is prevented from decreasing. do not have.

When the bubbles decrease, the valve 7 is closed, the ozone supply to the second dihydr user 6 is stopped, and the process can be continued using only the first dihy user 5.

FIG. 2 is a diagram showing the occurrence of bubbles in case A when the second dihyuser 6 is used and case B when it is not used.

That is, in case B, the height h of the bubbles is the height of the space above the water surface of the ozone reaction tank 1.

The temperature rises higher and the bubbles move to the ozone decomposition tank 11, but A
This shows that this can be prevented.

Note that the pores of the second dihyuser 6 are similar to those of the first dihyuser 5.
A more appropriate amount of ozone injection can be obtained by making the pore diameter smaller than that of the pores.

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 dihyuser that injects reactive ozone, there is a By installing a second dither user to decompose the foam near the water surface, which is often present at the beginning of the treatment operation, the foam is effectively defoamed.As a result, the foam increases and moves into the ozone decomposition tank, increasing the ozone decomposition ability. It is possible to prevent the deterioration.

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... Tank in which wastewater is stored, 5... First dihyuser, 6... Second dihyuser, 10... Ozone generator, 11 ...Ozone decomposition tank.

Claims (1)

[Claims] 1 A tank in which wastewater is stored; a first dihyuser installed in the lower part of this tank to send ozone into the wastewater as bubbles; and a first dihyuser installed near the surface of the wastewater in the tank to send ozone into the wastewater in the form of bubbles. A wastewater treatment device comprising a second dihyuser.