JPS6136480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewage treatment apparatus based on an activated sludge method, and particularly to an apparatus that can effectively treat a large amount of sewage using a treatment tank with a limited capacity. This device can also be applied when modifying an existing aeration tank to improve its processing capacity.

Wastewater treatment using the activated sludge method creates aerobic conditions by blowing air or oxygen into the wastewater to be treated in an aeration tank, and the BOD in the wastewater is reduced by the action of aerobic microorganisms.
This is generally done by decomposing the aerated liquid, then allowing the aerated liquid to stand still in a final settling tank to precipitate activated sludge, and then taking out the separated supernatant liquid as treated water. The aerobic microorganisms necessary for biological oxidation in the aeration tank are constantly replenished by returning the activated sludge that has been precipitated and separated in the final settling tank to the aeration tank; Even if it is done,
In the final sedimentation tank, the activity decreases due to the lack of oxygen, so it takes time to recover the activity after the water is sent back to the aeration tank, which is the reason why the treatment efficiency of the sewage treatment equipment as a whole decreases. It is becoming. In addition, the treatment capacity per unit volume is related to the density of activated sludge in the treatment tank, but in conventional methods, the sludge layer is vigorously agitated by bubbling to supply oxygen, and the concentration of dissolved oxygen is limited due to the limit of bubbling. However, increasing the sludge density would result in oxygen deficiency, making it impossible to significantly increase the sludge density and limiting treatment capacity.

The present invention was made to eliminate the drawbacks of conventional sewage treatment equipment as described above, and it maintains aerobic conditions throughout the entire sewage treatment process and increases the density of activated sludge. The object of the present invention is to provide a sewage treatment device that can treat a large amount of sewage even in a small-volume treatment tank by maintaining the amount of sewage.

An embodiment of the present invention will be explained below with reference to the drawings. In the figure, 1 indicates the tank body, and in this example, the existing aeration tank itself is used. Reference numeral 2 denotes a partition wall that divides the inside of the tank body 1 into a sludge zone 3 and a bubbler zone 4. The sludge zone 3 and the bubbler zone 4 communicate with each other via a passage 5 at the bottom of each, and a sewage supply pipe is installed near this passage 5. The tip of 6 is open. 7 is an overflow trough for overflowing the supernatant liquid. A diffuser 8 is provided at the bottom of the bubbler zone 4, and oxygen-containing gas supplied from a pipe 9 is blown into the liquid within the bubbler zone 4. The oxygen-containing gas may be air, but is preferably a high-concentration oxygen gas containing oxygen at a higher proportion than air. A settler pipe 10 extends diagonally downward from the top of the bubbler zone 4 to the bottom of the sludge zone 3, and its tip opens within the sludge zone 3 and at the furthest position from the bubbler zone 4. The settler pipe 10 is also provided with a branch 10a that extends downward from a midway position and opens at the center of the sludge zone 3. Reference numeral 11 indicates a buttful plate provided within the sludge zone 3.

By blowing oxygen-containing gas into the liquid in the bubbler zone 4 from the pipe 9 through the diffuser 8, the liquid rises due to the upwelling force of the bubbles, and at the same time, oxygen gas is dissolved in the liquid. The gas that is not absorbed by the liquid is separated from the liquid at the liquid level in the bubbler zone 4, a considerable portion of which is recovered from the pipe 12 and used for circulation, and a portion is discharged from the pipe 13 as exhaust gas. Foam generated on the liquid surface in the bubbler zone 4 is defoamed by water sprinkling from the defoaming pipe 14.

On the other hand, the liquid with increased dissolved oxygen concentration in the bubbler zone 4 entered the settler tube 10 after reaching the upper end of the bubbler zone 4, and more complete separation of bubbles was performed while flowing inside the settler tube 10. Thereafter, it flows into the sludge zone 3 from the tip of the settler pipe 10 and its branch 10a. This liquid movement is slowed down by the difference between the liquid level in the bubbler zone 4 and the liquid level in the sludge zone 3, forming two quiet flows in the sludge zone 3. One flow is
It descends from the tip of the settler tube 10, and then the tank body 1
The other flow goes up inside the sludge zone 3 along the side wall of the tank body 1 and flows between the sludge formed in the sludge zone 3 and the supernatant liquid. flows almost horizontally along the interface 15 of
This is a shear flow that circulates along a path toward the bottom of the
Due to these two flows, oxygen is smoothly supplied throughout the sludge zone 3 by the liquid with a high DO value that exits the settler pipe 10, and high aerobic conditions are maintained in all parts. Ru. Furthermore, branch 10
A is provided mainly to direct a part of the liquid in the settler pipe 10 to the bottom of the sludge zone 3 and to prevent sludge from stagnating in this part, and other stirring means are provided. It can be omitted if In addition, the full board 11 is connected to the sludge zone 3.
The sludge flow is provided downward in the portion where the sludge flow is upward, and prevents the sludge flow from disturbing the sludge interface 15. By changing the angle of this buff-full plate 11, it is possible to adjust the height of the interface 15 to some extent. Then, the supernatant liquid separated above the interface 15 flows into the overflow trough 7 at a flow rate commensurate with the inflow amount of new mud water supplied from the waste water supply pipe 6, and is taken out to the outside as treated water.

Furthermore, a damper 16 may be provided to adjust the flow rate of the liquid passing through the settler pipe 10 from the bubbler zone 4 to the sludge zone 3. When the damper 16 restricts the flow rate of the liquid flowing in the settler pipe 10, the residence time in the bubbler zone 4 becomes longer, assuming that the flow rate of the oxygen-containing gas blown from the diffuser 8 remains the same. amount of dissolved oxygen in the liquid leaving bubbler zone 4 by
DO increases. This means that even if the flow rate of liquid convecting within the sludge zone 3 is small, the sludge zone 3
This means that the necessary amount of oxygen can be supplied to maintain a sufficiently aerobic environment inside the tank, which improves the settling conditions of the sludge. According to the experimental results, when the residence time in bubbler zone 4 is 7 to 8 seconds, the DO
Under conditions where the
It has been confirmed that when extended to 30 seconds, DO increases to 12-14 ppm. Note that the optimal value of the flow rate of the liquid transferred from the bubbler zone 4 to the sludge zone 3 through the settler pipe 10 changes depending on various conditions, so in order to obtain the optimal flow rate, the damper 1
6 is desirably adjustable from the outside.

As described above, in the apparatus of the present invention, the liquid replenished with DO through contact with the oxygen-containing gas in the bubbler zone 4 is introduced into the sludge zone 3 through the settler pipe 10 at the farthest position from the bubbler zone 4. Then, by swirling the sludge in the sludge zone 3, oxygen is evenly distributed throughout the sludge zone 3, and an effective oxidation reaction of BOD in the sewage takes place. In addition, the liquid moves slowly from the bubbler zone 4 to the sludge zone 3, and the liquid moves from the bottom of the sludge zone 3 to the sludge zone 3. sludge will be present at a high density at the bottom. Therefore, even if the amount of generated sludge increases, the density can increase accordingly, so the sludge interface 15 becomes stable and there is no risk of sludge overflowing. It is possible to increase the density of this sludge even at a high concentration of 8000 ppm or more (for example, 1500 ppp). Moreover, since highly aerobic conditions are maintained with high MLSS concentrations, it is possible to perform denitrification and dephosphorization in addition to BOD removal.

[Brief explanation of the drawing]

The figure is a schematic vertical sectional view of a sewage treatment device according to an embodiment of the present invention. 1... Tank body, 2... Partition wall, 3... Sludge zone, 4...
Bubbler zone, 5... passage, 7... overflow trough, 8
... Diffuser, 10... Settler pipe, 10a... Branch, 11... Bumpful plate, 15... Interface, 16... Damper.

Claims (1)

[Scope of Claims] 1. A substantially vertically arranged partition wall that partitions the interior of the tank body into a sludge zone and a bubbler zone that are adjacent to each other; Oxygen-containing gas is provided by a passage formed at the lower end of the partition wall, a diff user disposed at the bottom of the bubbler zone and blowing oxygen-containing gas into the liquid in the bubbler zone, and gas bubbles blown from the diff user. a settler pipe that guides the liquid that has risen due to the upwelling force from the upper end of the bubbler zone to the part of the sludge zone that is farthest from the bubbler zone;
A buttress plate installed in the sludge zone so as to suppress upward spiral flow formed by the liquid in the sludge zone due to the liquid flowing out from the settler pipe, and a separated plate in the sludge zone. A sewage treatment device equipped with an overflow trough that discharges supernatant liquid by overflow. 2. The sewage treatment apparatus according to claim 1, further comprising a damper for adjusting the flow rate of liquid flowing from the bubbler zone to the sludge zone through the settler pipe.