JP3316959B2 - Biological sludge ozonation equipment - Google Patents

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 oxidizing biological sludge with ozone.

[0002]

2. Description of the Related Art For the purpose of reducing the volume of excess sludge in activated sludge treatment, biological sludge such as excess sludge (hereinafter sometimes referred to simply as sludge) is reacted with ozone to oxidatively decompose it. I have. In this case, when an ozone gas is blown into the sludge-containing liquid in the reaction tank to carry out the reaction, the sludge-containing liquid foams and easily causes a failure. In addition, the sludge floats and attaches to the upper part of the column as scum, or sediments at the lower part and accumulates, resulting in poor reaction efficiency. Therefore, a long residence time is required to sufficiently react sludge with ozone.

Conventionally, in order to prevent foaming trouble, an antifoaming agent is added, or a spray nozzle is provided in the upper part of the reaction tank, and industrial water or final treated water is sprayed from the nozzle as defoaming water on the liquid surface. And defoaming. However, in the method using an antifoaming agent, since the surface tension of the liquid is reduced, bubbles are associated with each other and the gas absorption efficiency is reduced, so that a large amount of ozone needs to be blown, and expensive ozone is discharged from the exhaust gas. There is a problem that it is discharged in large quantities. In the conventional method of spraying defoaming water, industrial water or final treated water is used as defoaming water. Therefore, it is necessary to increase the size of the reaction tank. Due to the dilution, the reaction rate between the mud and the ozone is reduced, and there is a problem that efficient treatment is not performed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biological sludge ozone treatment apparatus capable of preventing foaming disturbance in a reaction tank and efficiently treating the sludge with a small apparatus. It is.

[0005]

According to the present invention, there is provided a reaction tank for reacting a biological sludge-containing liquid with ozone, a liquid in the tank in the reaction tank is withdrawn, and the extracted liquid is sprayed on a liquid surface in the reaction tank. And a liquid spraying means for defoaming the sludge.

[0006] The biological sludge to be treated in the present invention is a sludge containing biological sludge generated in aerobic treatment, anaerobic treatment, etc., and is preferably sludge mainly composed of biological sludge such as excess sludge. It may contain some inorganic substances such as coagulated sludge. Such biological sludge contains solid matter,
Since it has adhesiveness, it has not been conventionally used for defoaming water.

[0007] The reaction tank constituting the ozone treatment apparatus of the present invention is a tank for causing an oxidation reaction by contacting ozone with sludge in a sludge-containing liquid. If the sludge is likely to settle in the reaction tank, or if there is more sludge to settle than the rising sludge, it is preferable to make the sludge-containing liquid and the ozone come into contact in parallel, whereby the sludge and The contact efficiency with ozone is improved. On the other hand, if the sludge is likely to float in the reaction tank, or if there is more floating sludge than settling sludge, it is preferable to make contact in countercurrent,
This improves the contact efficiency.

[0008] The liquid spraying means is for drawing out the liquid in the tank containing sludge in the reaction tank, and spraying the drawn liquid as defoaming water on the liquid surface in the reaction tank. If the sludge is likely to settle in the reaction tank, or if there is more sludge to settle than the sludge that floats, it is preferable to pull out the sludge from the lower part of the reaction tank where the sludge is settled. The contact efficiency with ozone is improved. On the other hand, if the sludge is likely to float in the reaction tank, or if there is more sludge to float compared to the settling sludge, it is preferable to pull out the sludge from the upper part of the reaction tank where the sludge is floating. The contact efficiency is improved.

The ozone treatment apparatus of the present invention is used as an apparatus for reducing the volume of an excess sludge by ozone treatment or for removing ozone from a biological treatment tank such as an aerobic treatment tank. it can.

[0010]

In the reaction tank, sludge reacts with ozone to be oxidatively decomposed and converted into BOD components. The bubbles generated at this time are
The liquid in the reaction tank is withdrawn and sprayed on the liquid surface to defoam. Withdrawing and spraying the sludge-containing liquid, including in the case of biological sludge, is not generally performed because solids easily block the nozzles. The present inventor has confirmed that the fineness is reduced and the adhesion is reduced, so that the nozzle or the like does not block.

In the present invention, since the liquid in the tank is used as the defoaming water, the amount of liquid in the tank does not increase as in the case where industrial water is used as the defoaming water. Become In addition, since the liquid in the tank is circulated and stirred by spraying, sludge sedimentation or floating is prevented, thereby improving the contact efficiency between ozone and sludge,
The efficiency of the whole ozone treatment is improved. In general, mixing the liquid in the upper part of the reaction tank with the liquid in the lower part reduces the concentration gradient, so such a mixing method is avoided, but the processing target is not a soluble substance but a solid such as sludge. In the case of,
As a result, the efficiency of the ozone treatment is increased.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a system diagram showing a sludge ozonation apparatus according to an embodiment. In the figure, reference numeral 1 denotes a reaction tank, and a liquid extraction passage 2 in the tank.
The liquid in the tank drawn out from 3 is configured to be sprayed onto the liquid surface from a spray nozzle 5 through a circulation path 4.

The reaction tank 1 is connected to a drain ozone passage 6 at the top of the tank, a treatment liquid introduction passage 7, a treatment liquid discharge passage 8, an in-tank liquid extraction passage 2 and a circulation passage 4 at the top. A spray nozzle 5 is connected to the circulation path 4 and is disposed on the liquid surface so that the liquid in the tank drawn from the liquid extraction paths 2 and 3 can be sprayed on the liquid surface.
An ozone introduction passage 9 and a liquid to be treated introduction passage 10 are provided at the bottom of the reaction tank 1, and a liquid extraction passage 3 and a treatment liquid discharge passage 1 are provided below the reaction tank 1.
1 is connected. Valves 12, 13, 14, 15, 16, and 17 are provided in the to-be-treated liquid introduction paths 7, 10, the treatment liquid discharge paths 8, 11, and the in-tank liquid extraction paths 2, 3, respectively. 18 is a pump.

In such an ozone treatment apparatus, when the liquid in the tank is withdrawn from the liquid withdrawal passage 2 in the tank connected to the upper part of the reaction tank 1, the liquid is drawn from a position near the liquid level above the liquid in the tank. Will be overtaken. On the other hand, when the in-tank liquid is withdrawn from the in-tank liquid extraction passage 3 connected to the lower part of the reaction tank 1, the liquid is to be withdrawn from a position near the bottom of the lower part of the in-tank liquid.

When treating a liquid containing buoyant sludge with the apparatus shown in FIG. 1, it is preferable to treat the liquid by countercurrent contact. In this case, in order to ozone-treat the liquid to be treated (sludge-containing liquid),
First, the valves 13, 14, 17 are closed, and the valve 12,
15 and 16 are opened. In this state, the liquid to be treated is introduced into the reaction tank 1 from the liquid introduction path 7 connected to the upper part of the reaction tank 1, and ozone or an ozone-containing gas is introduced from the ozone introduction path 9, and contact is made in countercurrent. Then, the sludge is oxidized and decomposed into BOD.

The pump 18 is driven to draw out the liquid in the tank from the liquid drawing passage 2 connected to the upper part of the reaction tank 1, and the drawn liquid is sprayed from the spray nozzle 5 to the liquid surface through the circulation path 4. . The drawing and spraying may be performed continuously or intermittently. The ozone exhaust gas is discharged from a discharge ozone path 6, and the ozone treatment liquid is discharged from a treatment liquid discharge path 11 connected to a lower portion of the reaction tank 1. Ozone treatment by countercurrent contact can be applied not only to the case where sludge floats in the reaction tank 1 but also to the case where more sludge floats than sludge that settles.

When the liquid containing sludge which tends to settle is treated with the apparatus shown in FIG. In this case, in order to ozone-treat the liquid to be treated, first, the valve 1
The valves 2, 15, and 16 are closed, and the valves 13, 14, 17 are opened. In this state, the liquid to be treated is introduced into the reaction tank 1 from the liquid introduction passage 10 connected to the lower portion of the reaction tank 1, and ozone or an ozone-containing gas is introduced from the ozone introduction passage 9, and contact is made in parallel. And ozone treated. The in-tank liquid is withdrawn from the in-tank liquid extraction passage 3 connected to the lower part of the reaction tank 1. The ozone treatment liquid is discharged from a treatment liquid discharge passage 8 connected to the upper part of the reaction tank 1. Other operations are performed in the same manner as in the case of countercurrent contact. The ozone treatment by the co-current contact can be applied not only to the case where sludge settles in the reaction tank 1 but also to the case where more sludge settles than sludge that floats.

In any of the above-mentioned treatments, the generated foam is eliminated by spraying the extracted liquid obtained by extracting the liquid in the tank on the liquid surface, thereby preventing foaming trouble. In addition, since the liquid in the tank is circulated and stirred, the contact efficiency between the sludge and the ozone is increased, thereby increasing the efficiency of the ozone treatment. Moreover, the efficiency of the ozone treatment is further increased because the tank solution is not diluted as in the case where industrial water is used as defoaming water. Further, since no defoaming agent is used, bubbles are not associated with each other, so that gas-liquid absorption efficiency is increased, and the amount of ozone used can be reduced.

By the ozone treatment and the agitation by the pump, the sludge is usually finely reduced to about 0.1 mm and the adhesion is reduced. Therefore, even if such a liquid in the tank is sprayed from the spray nozzle 5, the spray nozzle 5 is not blocked. On the other hand, when the sludge-containing liquid that is not subjected to the ozone treatment is sprayed from the spray nozzle, the spray nozzle is blocked by the solid matter, so that the liquid in the tank that is not subjected to the ozone treatment cannot be used as defoaming water.

The apparatus shown in FIG. 1 can be applied to either the countercurrent contact or the cocurrent contact. However, the unnecessary flow path is omitted, and the apparatus is applied to either the countercurrent contact or the cocurrent contact. Can be a device.

Next, test examples will be described. Example 1 A column having an inner diameter of 100 mm and a height of 5000 mm was used as a reaction tank, and municipal sewage sludge having a sludge concentration of 10,000 mg / l was treated with ozone at a flow rate (SV, the same applies hereinafter) of 2 h ^-1 . Ozone treatment, ozone gas concentration 20mg
/ L of ozone-containing gas was used for countercurrent contact, and the solution in the tank was withdrawn from a position 1 m from the top of the column and circulated by a pump to spray. As a result, the flow rate of the ozone-containing gas at the time when the ozone consumption reached 0.12 g-O ₃ / g-SS was 3 min ^-1 . The result is 1
This indicates that the ozone-containing gas was discharged as exhaust gas at a rate of min ^-1 .

Example 2 An ozone treatment was performed in the same manner as in Example 1 except that the contact method was changed to co-current contact. As a result, the flow rate of the ozone-containing gas at the time when the ozone consumption reached 0.12 g-O ₃ / g-SS was 3.5 min ^-1 .

Comparative Example 1 In Example 1, the application of the liquid in the tank was stopped, and ozone treatment was performed. As a result, the sludge settles, and it is necessary to increase the flow rate of the ozone-containing gas to 4 min ^{-1 in order} to reduce the ozone consumption to 0.12 g-O ₃ / g-SS. This result indicates that the ozone-containing gas was discharged as exhaust gas at a rate of 2 min ^-1 . In this case, when the flow rate of the gas is 1.2 to 1.3 min ^-1 (0.05 g-O ₃ / g-SS as the consumption of ozone) or more, foaming becomes intense, and the liquid in the tank overflows into the exhaust gas line. In order to avoid this, an empty tower had to be newly provided 2 m.

Comparative Example 2 In Example 1, when municipal sewage sludge that had not been subjected to ozone treatment was used as the defoaming water instead of the liquid in the tank, the spray nozzle was blocked and spraying became impossible.

Example 3 In Example 1, the sludge concentration was 10000 as the liquid to be treated.
Ozone treatment was carried out in the same manner as in Example 1 except that mg / l night soil sludge was used, the contact method was parallel flow contact, and the withdrawal position of the liquid in the tank was changed to a position 1 m from the lower end of the column.
As a result, the ozone consumption is 0.12 g-O ₃ / g-S
The flow rate of the ozone-containing gas at the time of reaching S was 3 min ^-1 .

Example 4 The same operation as in Example 3 was carried out except that the position for extracting the liquid in the tank was changed to a position 2 m from the lower end of the column. as a result,
Consumption of ozone flow rate of the ozone-containing gas at the time of a 0.12g-O ₃ / g-SS was 4min ^-1.

Example 5 The same operation as in Example 3 was carried out except that the position for extracting the liquid in the tank was changed to a position 3 m from the lower end of the column. as a result,
The flow rate of the ozone-containing gas at the time when the ozone consumption reached 0.12 g-O ₃ / g-SS was 5.5 min ^-1 .

Comparative Example 3 In Example 3, when non-ozone treated urine sludge was used instead of the liquid in the tank as the defoaming water, the spray nozzle clogged and spraying became impossible.

Comparative Example 4 In Example 3, when the spraying of the liquid in the tank was stopped and the ozone treatment was performed, the sludge floated as scum and overflowed into the exhaust gas line, so that the operation could not be performed.

Comparative Example 5 In Comparative Example 4, the operation was possible if an antifoaming agent was added, but the ozone consumption was reduced to 0.12 g-O ₃ / g-SS.
To achieve this, the flow rate of the ozone-containing gas had to be increased to 8 min ^-1 .

Comparative Example 6 In Comparative Example 4, when defoaming was performed using tap water, the flow rate of the ozone-containing gas was reduced to 6 min ^{-1 in order} to reduce the ozone consumption to 0.12 g-O ₃ / g-SS. I needed to make it bigger.

[0032]

According to the present invention, the liquid in the ozone reaction tank is used as defoaming water and is sprayed on the liquid surface, so that foaming of the liquid to be treated can be effectively performed without blocking the nozzle. Thus, a sludge ozonation apparatus capable of preventing the sludge and efficiently treating the sludge with a small apparatus can be obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a sludge ozonation apparatus according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank 2, 3 Liquid extraction path in tank 4 Circulation path 5 Spray nozzle 6 Discharge ozone path 7, 10 Liquid to be treated introduction path 8, 11 Treatment liquid discharge path 9 Ozone introduction path 12, 13, 14, 15, 16, 17 Valve 18 Pump

Claims (1)

(57) [Claims] 1. A reaction tank for reacting a biological sludge-containing liquid with ozone, and a liquid spraying means for drawing out a liquid in the tank in the reaction tank and spraying the drawn liquid on a liquid surface in the reaction tank to defoam the liquid. An ozone treatment apparatus for biological sludge, comprising: