JPS6135919B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an activated sludge treatment apparatus having an ultra-deep aeration tank. Recently, an ultra-deep aeration tank with a water depth of 50 to 150 m has been developed, in which a descending channel and an ascending channel are interconnected at their upper and lower ends. Since such equipment has a large oxygen dissolving capacity, it has become possible to save energy and reduce the site area. When performing activated sludge treatment in this ultra-deep aeration tank, air blown into the downward flow path descends with the water flow, dissolves to its maximum at the bottom of the tank due to increased water pressure, and then rises through the upward flow path. As the water pressure decreases, excess dissolved matter becomes fine bubbles and precipitates out. At this time, fine air bubbles adhere to the activated sludge floc surface, so even if you try to separate the activated sludge and treated liquid into solid-liquid in a normal settling tank, some of the activated sludge will float up and flow out together with the treated water. The quality of treated water deteriorates. As a solution to this problem, the following two types of solid-liquid separation methods have been proposed in the past: (1) Solid-liquid separation of the mixture of activated sludge and treated liquid flowing out from the ultra-deep aeration tank using a flotation separator; . (2) The mixed liquid flowing out from the ultra-deep aeration tank is reduced in pressure with a vacuum pump and passed through a vacuum deaeration tower, where it is degassed, and then solid-liquid separation is performed in a normal settling tank. However, in method (1), the amount of blown air is determined according to the load, or the mixed liquid is determined so that it circulates through the downward flow path and the upward flow path, so the amount of activated sludge and the amount necessary for flotation are determined. The number of bubbles cannot necessarily maintain a stable constant ratio. Therefore, some of the activated sludge may not float due to insufficient number of bubbles. In addition, bubbles may come together to form large bubbles, and these large bubbles may have a high floating speed and destroy the floating layer of activated sludge. Furthermore, flotation separation may not be possible due to physical properties such as specific gravity, hydrophilicity, and hydrophobicity of activated sludge flocs. In this way, it was difficult to perform stable flotation separation, and activated sludge sometimes got mixed into the treated water. On the other hand, method (2) has very good deaeration efficiency;
It is currently the best method to perform high-grade solid-liquid separation operations and to obtain stable, high-quality treated water. However, the equipment is complicated, such as requiring a vacuum pump, and requires skilled operating techniques. Therefore, it is desired to develop an activated sludge treatment apparatus having an ultra-deep aeration tank equipped with simple and easy-to-operate deaeration equipment. An object of the present invention is to eliminate the drawbacks of the prior art and provide an ultra-deep aeration tank equipped with deaeration equipment that can achieve deaeration efficiency comparable to that of a vacuum deaeration tower through simple and easy operations. An object of the present invention is to provide an activated sludge treatment device having the following features. According to the present invention, this purpose is achieved by installing a collision plate between the ultra-deep aeration tank and the solid-liquid separation tank, which causes the mixed liquid of activated sludge and treated liquid flowing out from the ultra-deep aeration tank to collide using a water level difference. This is achieved by installing a deaeration tank with multiple stages. That is, according to the present invention, the air bubbles contained in the mixed liquid of activated sludge and treatment liquid are dissipated from the liquid by the impact when it falls onto the collision plate, so that by repeating the collision, the mixed liquid can be sufficiently Can be degassed. Since it is sufficient to provide a collision surface for the bubbles, the collision plate may be made of any material such as wood, metal, or plastic, and its structure may be flat, perforated, or mesh. It may be a plate in the form of a grid or a grid, or a plate having protrusions or irregularities on its surface. The amount of water that causes the mixed liquid to collide is per unit collision area.
0.05 to 0.4 m ³ /m ² /S is good. Advantageously, the spacing between the collision plates is 20 to 60 cm, and the number of collision plates is 5 to 30 stages. Below these values, the deaeration will be reduced, and above these, the sludge flocs will be destroyed, pin flocs will float in the subsequent settling tank, or no significant improvement in the deaeration effect can be expected. That is, the position, interval, and number of stages of the collision plates are determined so as to sufficiently dissipate air bubbles in the mixed liquid, but not to destroy the sludge flocs. Next, the present invention will be explained in detail based on the drawings. The drawing is an explanatory diagram of one embodiment of the activated sludge treatment apparatus of the present invention. The activated sludge treatment apparatus according to the present invention includes an ultra-deep aeration tank 1, a deaeration tank 13, and a settling tank 12. The ultra-deep aeration tank 1 consists of an upward flow path 2, a downward flow path 3, and a head tank 5. The supply of oxygen necessary for aerobic biological treatment and the stirring of microorganisms and sewage are carried out by blowing air and water flow from a circulation pump 6. It is carried out with Air is sent into the descending flow path 2,
This causes a difference in the total bubble volume (porosity) in the upward flow path 3 and the downward flow path 2, and the circulation pump 6 is used as the driving force to circulate the mixed liquid of activated sludge and treatment liquid, and at the same time, oxygen is mixed. Dissolves in liquid. At this time, the air blown into the descending channel 2 by the compressor 4 dissolves to the maximum at the bottom of the tank due to the increase in water pressure, and then as it ascends the ascending channel 3, the excess dissolved content is removed by the decrease in water pressure. Precipitates as fine bubbles. At this time, since the fine air bubbles adhere to the activated sludge floc surface, a simple deaeration equipment is required that can easily and efficiently remove the fine air bubbles from the activated sludge floc surface. Therefore, in the present invention, the deaeration tank 13 has a plurality of stages of collision plates 14 in order to cause the mixed liquid of activated sludge and treatment liquid flowing out from the ultra-deep aeration tank 1 to collide based on the water level difference. In this deaeration tank 13, the first-stage collision plate 14 is positioned lower than the water level of the head tank 5 of the ultra-deep aeration tank 1, and is mounted perpendicularly or downward to the wall of the deaeration tank, and then moved 20 to 60 cm downward in order.
5 to 30 steps will be installed with a difference in steps. Deaeration tank 13
The top of the is open. The liquid mixture flowing out of the head tank 5 collides with each collision plate 14 in order from above and is agitated, and fine bubbles are separated from the liquid and released from the upper part of the degassing tank 13. The mixed solution sufficiently deaerated in this way is then sent to the sedimentation tank 12, where the sludge flocs in the mixed solution are easily separated by a normal sedimentation method. Sedimentation pond 12
The sludge settled at the bottom of the tank is returned to the ultra-deep aeration tank 1 by a sludge return pump 8. As described above, according to the present invention, sufficient deaeration can be achieved with extremely simple equipment, so it is possible to avoid obstacles to solid-liquid separation caused by floating sludge due to air bubbles, and it is possible to stably obtain treated water of good quality. . Next, the present invention will be described in detail based on Examples, but the present invention is not limited thereto. Example Using an activated sludge treatment device according to the present invention with underground water shown in the drawing and an activated sludge treatment device having an ultra-deep aeration tank equipped with a conventional vacuum degassing tower, the operation was carried out under the operating conditions shown in Table 1. Processed. Suspended solids (SS), mainly activated sludge, and BOD in the treated water were measured, and the results are shown in Table 2.

【table】

[Table] As can be seen from the above table, the present invention provides a degassing effect comparable to that of the conventional activated sludge treatment equipment equipped with a vacuum degassing tower, and solid-liquid separation is easily carried out. We were able to obtain high quality treated water that is equivalent to the quality of treated water.

[Brief explanation of the drawing]

The drawing is an explanatory diagram of the activated sludge treatment apparatus of the present invention. Explanation of symbols, 1... Ultra-deep aeration tank, 2... Downflow channel, 3... Upflow channel, 12... Sedimentation basin, 13...
... Deaeration tank, 14... Collision plate.

Claims (1)

[Claims] 1. Activated sludge consisting of an ultra-deep aeration tank in which a downward flow path and an upward flow path are interconnected at their upper and lower ends, and a solid-liquid separation tank section that separates activated sludge and treated liquid. In the treatment equipment, between the ultra-deep aeration tank and the solid-liquid separation tank, there are multiple stages of collision plates that collide the mixed liquid of activated sludge and treatment liquid flowing out from the ultra-deep aeration tank using a water level difference. An activated sludge treatment device characterized by being equipped with a deaeration tank. 2. The device according to claim 1, wherein the collision plate is a flat plate, a perforated plate, a plate with a mesh or lattice-like plane, or a plate having protrusions or irregularities on the surface. 3. The device according to claim 1, wherein the collision plate is attached perpendicularly or downwardly inclined to the wall surface of the degassing tank. 4. The device according to claim 1, wherein 5 to 30 stages of collision plates are provided at intervals of 20 to 60 cm.