JPH07232184A - Ozone treating device for biological sludge - Google Patents

Abstract

PURPOSE:To provide an ozone treating device for biological sludge capable of making the sludge into BOD by inexpensively and efficiently treating the biological sludge by ozone. CONSTITUTION:The sludge is decomposed by oxidation and foamed by blowing an ozone containing gas 14 to a liquid phase contact zone 3 of a reaction vessel 1 to form a foam contact zone 4 having >=1m height on the top part of the liquid contact zone 3, where gas-liquid contact is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological sludge ozone treatment apparatus for ozone-oxidizing biological sludge.

[0002]

2. Description of the Related Art For the purpose of reducing the volume of surplus sludge and the like in activated sludge treatment, biological sludge such as surplus sludge (hereinafter sometimes simply referred to as sludge) is reacted with ozone for oxidative decomposition. ing. In the conventional ozone treatment method for sludge, a device is used in which the reaction tank is filled with a sludge-containing liquid, and ozone-containing gas is blown into the sludge-containing liquid to bring them into gas-liquid contact to decompose the sludge. In conventional devices, the gas-liquid contact area is small, so it is necessary to lengthen the residence time in order to sufficiently react sludge with ozone.
In addition, there is a problem that efficient processing cannot be performed, such as wasteful consumption of expensive ozone. Although it is possible to increase the gas-liquid contact area and improve the processing efficiency by mechanically stirring the liquid to be processed, in this case, there is a problem that the processing cost becomes high.

By the way, when ozone-containing gas is blown into the sludge-containing liquid in the reaction tank for ozone treatment, the sludge-containing liquid is foamed, and the foam is likely to be taken out of the tank. For this reason, conventionally, defoaming was performed by adding an antifoaming agent, or a spray nozzle was installed in the upper part of the reaction tank, and industrial water or final treated water was sprayed on the liquid surface from this nozzle to defoam, resulting in foaming failure. Is being prevented. As described above, in the conventional sludge ozone treatment method, the ozone treatment is performed while suppressing the foaming as much as possible, and the ozone treatment utilizing the foaming has not been performed so far.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ozone treatment apparatus for biological sludge, which is capable of efficiently ozone treating biological sludge at low cost.

[0005]

The present invention is directed to a reaction tank for receiving a biological sludge-containing liquid for ozone treatment, and a liquid for blowing ozone-containing gas into the gas-liquid contact in the biological sludge-containing liquid in the reaction tank. A biological sludge comprising a phase contact area and a foam contact area for forming gas-liquid contact by forming a foam layer of 1 m or more in the upper part of the liquid phase contact area by blowing ozone-containing gas. It is an ozone treatment device.

[0006] By the following procedure, the foam layer is maintained.
It is preferable because it can be controlled. (A) The biological sludge concentration of the biological sludge-containing liquid is 2,000 to 2
If it is set to 20,000 mg / l, it is easy to maintain the foam layer. (B) If a foam holding member is installed in the foam contact area of the reaction tank, it is easy to maintain the foam layer. (C) If a liquid spraying device for spraying the liquid is installed above the foam contact area of the reaction tank, it is easy to control the height of the foam layer. (D) When the biological sludge-containing liquid in the reaction tank is used as a part of the spray liquid of the liquid spraying device and the liquid is circulated and sprayed, the height of the foam layer can be easily controlled and ozone can be effectively used.

The biological sludge to be treated in the present invention is a sludge containing biological sludge produced in aerobic treatment, anaerobic treatment and the like, and it is preferable to mainly use biological sludge like surplus sludge, It may be one that contains a small amount of inorganic substances such as coagulated sludge. The biological sludge concentration in the biological sludge-containing liquid is 2,000 to 20,000 mg / l, preferably 5,0.
It is preferably from 0 to 15,000 mg / l. In this range, the height of the foam layer can be maintained at 1 m or more by selecting the foaming conditions such as the ozone flow rate, the spray flow rate, the presence or absence of the foam holding member.

The reaction tank used for the ozone treatment in the present invention is a tank for reacting sludge in the sludge-containing liquid with the ozone-containing gas for oxidation treatment. A liquid-phase contact region for blowing gas into liquid is formed, and a foam contact region for contacting the foamed foam and the ozone-containing gas is formed on the liquid-phase contact region. The height of the liquid phase contact area is 0.2 to 3 m, preferably 0.5 to 1.5 m
And The height of the foam contact area may be 1 m or more above the liquid level of the sludge-containing liquid in the liquid phase contact area, but preferably 1
The height is set to 10 m, more preferably 2 to 5 m.

It is preferable to maintain the liquid phase contact area at a substantially constant height. For example, an overflow type in-tank liquid outlet is provided in the lower or middle part of the reaction tank so that the liquid level in the tank is constant. Can be kept at. It is preferable that the foam contact area is formed in a space above the liquid surface in the liquid phase contact area (liquid outlet in the tank).

The foam contact area can be filled with a foam holding member, whereby when the inner diameter of the reaction tank is large and it is difficult to hold the foam, or when the concentration of the biological sludge is low, the sludge-containing liquid hardly foams. Even in such a case, the foam can be efficiently retained and the ozone treatment efficiency can be increased. The foam holding member may have a structure capable of holding foam, but a partition plate structure such as a honeycomb shape or a lattice shape is preferable.

As the ozone-containing gas, ozone-containing air,
Ozonized air can be used. The amount of ozone introduced is preferably 1 to 10%, and more preferably 3 to 5%, with respect to the VSS weight of the biological sludge to be introduced. The flow rate of the ozone-containing gas is 5 to 50 m / in terms of the linear gas velocity in the reaction tank.
It is preferably set to hr, preferably 10 to 30 m / hr.

A liquid spraying device is provided above the foam contact area in the reaction tank, and industrial water, the final treatment liquid, the drawing liquid from the reaction tank, or the mixed liquid of the drawing liquid and the liquid to be treated is put into the foam layer. It can be sprayed towards, thereby suppressing excessive foaming and maintaining the foam contact area at a predetermined height. In this case, it is preferable to use a drawing liquid or a mixed liquid of the drawing liquid and the liquid to be treated because the sludge concentration of the liquid in the tank does not decrease.

It should be noted that, including the case of biological sludge, it is not generally practiced to draw out and spray the sludge-containing liquid, because solid matter easily clogs the nozzle, but it is a system for treating biological sludge with ozone. Then, the present inventor has confirmed that, since the biological sludge is miniaturized and the adhesiveness is reduced, the nozzle and the like are not clogged even when the liquid in the tank is sprayed. Also, since the liquid to be treated is diluted even with a mixed liquid of the liquid in the bath and the liquid to be treated, the nozzles and the like are hardly clogged, but if the liquid to be treated not subjected to ozone treatment is used alone, the nozzles are easily clogged. It is preferable not to use it for spraying.

Since the foam contact area of the ozone treatment apparatus of the present invention is only filled with foam, the strength of the reaction tank may be smaller than that of the apparatus which fills the reaction tank with the liquid to be treated, and the apparatus is low in cost accordingly. Become. INDUSTRIAL APPLICABILITY The ozone treatment apparatus of the present invention can be used when ozone treatment is performed on excess sludge to reduce its volume, or when a mixed solution in the tank is drawn out from a biological treatment tank, for example, an aerobic treatment tank, for ozone treatment.

In the reaction tank, sludge reacts with ozone to be oxidatively decomposed and converted into BOD components. The sludge-containing liquid (in-tank liquid) that has been subjected to the ozone treatment has an increased viscosity and becomes a liquid having a very high foaming property. Therefore, when the sludge-containing liquid and the ozone-containing gas are brought into contact with each other, they easily foam to form a foam layer. In the present invention, since the foam layer is formed so as to be brought into contact with the ozone-containing gas, the sludge present in the liquid in the tank becomes a foam in a state of being in contact with ozone, and further in contact with ozone in a state of foam. It is disassembled and repeated. Therefore, the efficiency of ozone treatment is higher than that in the case of contacting only in the liquid phase contact area. Also, if the ozone-containing gas is contacted only in the foam contact area, the ozone-containing gas easily passes through the foam layer by channeling, but by blowing it into the liquid-phase contact area, the ozone-containing gas is made into fine bubbles to improve the contact efficiency and form the foam layer. can do.

When the foam retaining member is filled in the foam contact area,
Even if the reaction vessel has a large inner diameter and it is difficult to retain the foam, or if the biological sludge-containing liquid does not easily foam, it is possible to retain the foam satisfactorily. It becomes possible to form and perform ozone treatment.

[0017]

The present invention will now be described with reference to the embodiments of the drawings.
1 to 3 are system diagrams showing an ozone treatment apparatus for biological sludge according to different embodiments, and FIGS. 4A and 4B are cross-sectional views taken along the line AA of FIG. In FIG. 1, reference numeral 1 is a reaction tank, in which a liquid (biological sludge-containing liquid) 2 in the tank is accommodated in a lower portion to form a liquid phase contact area 3. The upper part of the liquid surface of the liquid phase contact area 3 is a foam contact area 4, and the in-tank liquid 2 is foamed to form a foam layer 5.

A circulation path 7 is connected to the reaction tank 1 so as to draw the in-tank liquid 2 from the lower liquid-phase contact area 3 and circulate it above the foam contact area 4, and a circulation pump 8 is provided in the middle thereof. A spray nozzle 9 is provided at the tip. In the middle of the circulation path 7, a liquid to be treated introduction path 11 having a liquid supply pump 10 is connected. Liquid phase contact area 3 under reaction tank 1
In the tank, a liquid discharge passage 1 having a siphon breaker 12 is provided.
3 is connected. An ozone-containing gas introducing passage 14 for blowing an ozone-containing gas into the liquid phase contact area 3 is connected to the bottom of the reaction tank 1, and an exhaust ozone gas passage 15 for discharging exhaust ozone gas is connected to the top.

In FIG. 2, the liquid to be treated introduction path 11 is shown in the reaction tank 1.
, And the circulation path 7 is connected to a position close to the bottom and far from the liquid surface in the liquid phase contact area 3. Other configurations are the same as those in FIG. In FIG. 3, the foam holding member 16 is provided in the foam contact area 4. The foam holding member 16 is shown in FIG.
A partition plate having a honeycomb shape as shown in (a) or a lattice-shaped cross-sectional shape as shown in (b), the cells 17 of which are arranged so as to be vertically oriented. There is. Other configurations are the same as those in FIG.

In order to treat the liquid to be treated with ozone by the apparatus shown in FIG. 1, the liquid supply pump 10 is driven to introduce the liquid to be treated 11 into the liquid to be treated.
While supplying the liquid to be treated from the inside, the circulation pump 8 is driven to draw out the in-tank liquid 2 from the circulation path 7 and circulate it. In this way, the liquid to be treated and the drawing liquid are mixed in the circulation path 7, and the mixed liquid is sprayed from the spray nozzle 9 toward the foam layer 5. Thereby, the liquid to be treated is introduced into the reaction tank 1, and the height of the foam layer 5 is adjusted so that the foam contact area 4 maintains a predetermined height.

On the other hand, the ozone-containing gas is introduced from the ozone-containing gas introduction passage 14 and blown into the tank liquid 2, whereby the tank liquid 2 and the ozone-containing gas are brought into contact with each other in the liquid phase contact area 3 to remove sludge. A foam layer 5 is formed in the foam contact area 4 by being oxidatively decomposed and foamed. The ozone-containing gas rising in the foam contact area 4 also contacts the sludge in the foam layer 5 and decomposes the sludge. In this case, the ozone-containing gas blown into the liquid-phase contact area 3 foams in a state of reacting with the sludge, enters the foam layer 5 as it is, and further reacts with the sludge, and the sludge-containing liquid forming the foam layer 5 is ozone. With the release of the contained gas, it returns to the liquid-phase contact region 3 as droplets, and this is repeated. Since the foam layer 5 has a large surface area, the gas-liquid contact efficiency is high, and therefore, the treatment efficiency is higher than that in the case where no foam is formed.
Further, since the load on the foam layer 5 is small, the strength of the reaction tank 1 may be small.

The ozone exhaust gas separated from the foam contact area 4 is directly raised and discharged from the exhaust ozone gas passage 15.
A part of the in-tank liquid 2 is used as an ozone treatment liquid, and the in-tank liquid discharge path 13
Discharge from. At this time, since the siphon breaker 12 is open to the atmosphere, the in-tank liquid 2 is discharged in an overflow manner, and the liquid level in the liquid phase contact area 3 is kept constant.

When the liquid to be treated containing sludge is introduced from the upper part of the reaction tank 1 and brought into contact with the ozone-containing gas in a countercurrent, the contact efficiency is improved as compared with the case where the liquid to be treated is introduced from the lower part and brought into parallel flow contact. Ozone treatment can be performed more efficiently. The liquid to be treated introduction path 11 may be directly connected to the reaction tank 1 in the range from the upper part of the reaction tank 1 to the upper part of the liquid phase contact area 3 without being connected to the circulation path 7.

In the case of FIG. 2, the liquid to be treated is introduced into the lower part of the liquid phase contact region 3 of the reaction tank 1 to be brought into contact with the ozone-containing gas in a parallel flow, and the liquid is withdrawn from the lower part of the liquid 2 in the tank and circulated. Other than the above, the same processing as in the case of FIG. 1 is performed.

In the case of FIG. 3, ozone treatment is performed in the same manner as in the case of FIG. In this case, since the honeycomb-shaped foam holding member 16 is provided in the foam contact area 4, even when foaming is difficult, the foamed foam adheres to the foam holding member 16 to form the foam layer 5 having a constant height. Hold and make foam contact. Therefore, ozone treatment can be performed efficiently.

Test Example 1 With the apparatus of FIG. 1, the height of the foam layer 5 is 0 to 2.0.
m, the depth of the in-tank liquid 2 was set to 4.0 to 2.0 m, and ozone-containing gas was blown into the activated sludge-containing liquid under the following conditions for ozone treatment. Results are shown in FIG. Activated sludge concentration in treated liquid: 7000 mg / l Flow rate of treated liquid: 100 ml / min Ozone concentration: 20 mg / l Ozone-containing gas flow rate: 1400-2400 ml / min Spray flow rate: 600 ml / min Inner diameter of reaction tank: 10 cm Total height of reaction tank: 4.3 m

From the results shown in FIG. 5, it can be seen that when the height of the foam layer 5 is 1 m or more, the ozone absorption efficiency is dramatically increased to 90% or more, and the ozone treatment can be efficiently performed.

Test Example 2 Using the apparatus shown in FIG. 2, ozone-containing gas was blown into activated sludge-containing liquids having different activated sludge concentrations, and ozone treatment was carried out under the following conditions. Results are shown in FIG. Activated sludge concentration in the liquid to be treated: 1000-7000 mg /
l Flow rate of liquid to be treated: 100 ml / min Ozone concentration: 20 mg / l Ozone-containing gas flow rate: 2000 ml / min Spray flow rate: 1000 ml / min (however, when activated sludge concentration is 2000 mg / l or more) Inner diameter of reaction tank : 10 cm Total height of reaction tank: 4.3 m Height of foam layer: 0-4 m

As can be seen from the results of FIG. 6, when the activated sludge concentration exceeded 2000 mg / l, the ozone absorption efficiency increased in proportion to the activated sludge concentration. The activated sludge concentration is also proportional to the height of the foam layer 5, and when the concentration is 4000 mg / l, the height of the foam layer exceeds 1 m and when it is 7000 mg / l, it is 4 m.
Became.

Test Example 3 Ozone-containing gas was blown into the activated sludge-containing liquid by the apparatus shown in FIG. 3, and ozone treatment was carried out under the following conditions. Foam holding member 16
A honeycomb-shaped partition plate having a pitch of 20 cm was used. As a result, the foam layer 5 had a height of 2 m above the water surface, and the ozone absorption efficiency at this time was 90%. Activated sludge concentration in treated liquid: 7000 mg / l Flow rate of treated liquid: 10 l / min Ozone concentration: 20 mg / l Ozone-containing gas flow rate: 200 l / min Spray flow rate: 20 l / min Reaction vessel inner diameter: 100 cm Total height of reaction tank: 4 m

Test Example 4 Test Example 3 was carried out in the same manner as Test Example 3 except that a honeycomb partition plate having a 10 cm pitch was used instead of the honeycomb partition plate having a 20 cm pitch. As a result, the height of the foam layer 5 rose to a height of 3 m above the water surface. At this time, the ozone absorption efficiency reached 99%.

Comparative Example 1 In Test Example 3, ozone treatment was performed without filling the partition plate. As a result, the foam layer 5 was held only at a height of about 0.5 m, and the ozone absorption efficiency was 80%.

[0033]

In the ozone treatment apparatus for biological sludge of the present invention, since the ozone-containing gas is blown into the liquid phase contact area in the reaction tank to foam, the foam contact area is formed above the liquid phase contact area. The biological sludge-containing liquid can be efficiently brought into contact with the ozone-containing gas by using the reaction tank having low strength, and thus the biological sludge can be efficiently ozone-treated at low cost.

Further, when the foam holding member is provided in the foam contact area, the foam can be held efficiently, and even if the foam is difficult to hold or foam, the biological sludge can be ozone-treated efficiently at low cost. can do.

Further, when the biological sludge-containing liquid is sprayed on the upper part of the foam contact area of the reaction tank, the foam contact area can be easily adjusted to a constant height.

[Brief description of drawings]

FIG. 1 is a system diagram showing an ozone treatment apparatus for biological sludge according to an embodiment.

FIG. 2 is a system diagram showing an ozone treatment apparatus for biological sludge according to another embodiment.

FIG. 3 is a system diagram showing an ozone treatment apparatus for biological sludge according to still another embodiment.

4 is a cross-sectional view taken along the line AA of FIG.

5 is a graph showing the results of Test Example 1. FIG.

FIG. 6 is a graph showing the results of Test Example 2.

[Explanation of symbols]

 1 Reaction tank 2 Liquid in tank 3 Liquid phase contact area 4 Foam contact area 5 Foam layer 7 Circulation path 8 Circulation pump 9 Spray nozzle 10 Liquid feed pump 11 Liquid to be treated introduction path 12 Siphon breaker 13 Liquid discharge path in tank 14 Ozone-containing Gas introduction path 15 Exhaust ozone gas path 16 Foam holding member 17 Cell

Claims (1)

[Claims] 1. A reaction tank for receiving a biological sludge-containing liquid for ozone treatment, a liquid-phase contact area for injecting an ozone-containing gas into the liquid-liquid contact in the biological sludge-containing liquid in the reaction tank, and an ozone-containing gas And a foam contact area for forming a foam layer of 1 m or more in the upper part of the liquid phase contact area to make gas-liquid contact by the blowing of the above.