JPS6136479B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewage treatment method based on an activated sludge method, and particularly to a method that can effectively treat a large amount of sewage using a treatment tank with a limited capacity. This method is effective in improving the capacity of existing aeration tanks.

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 causes the overall treatment efficiency of the sewage treatment system to decrease. It's summery. 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 methods 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 wastewater treatment method that can treat a large amount of wastewater even in a small-volume treatment tank by maintaining the amount of wastewater.

Hereinafter, the sewage treatment method of the present invention will be explained 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 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 flows into the settler tube 10 after reaching the upper end of the bubbler zone 4, and more complete separation of bubbles is performed while flowing inside the settler tube 10. Afterwards, 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 current that circulates along the path toward the bottom of the surface.
Through these two flows, oxygen is smoothly supplied to the entire area within 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. . Furthermore, branch 10a
A part of the liquid in the settler pipe 10 is transferred to the sludge zone 3.
The main purpose is to prevent sludge from stagnating in this area towards the bottom of the tank.
It can be omitted if other stirring means are provided. Further, the baffle plate 11 is provided downward in a portion of the sludge zone 3 where the shear flow is upward, and prevents the shear 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.

As described above, according to the method of the present invention, the liquid replenished with DO through contact with the oxygen-containing gas in the bubbler zone 4 passes through the settler pipe 10 and enters the sludge zone 3 at the farthest position from the bubbler zone 4. Then, by swirling within this sludge zone 3, oxygen is evenly distributed throughout the sludge zone 3, and an effective oxygen 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 sludge zone 3 to the bubbler zone 4 from the bottom of the sludge zone 3.
In the sludge zone 3, sludge is present at a high density at the bottom of the sludge zone 3. 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. The densification of this sludge is
A high concentration of 8,000 ppm or more (for example, 15,000 ppp) is also possible. 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 longitudinal sectional view of an apparatus applied to carry out the method of the invention. 1... Tank body, 2... Partition wall, 3... Sludge zone, 4...
Bubbler zone, 5... passage, 7... overflow trough, 8
... Diffuser, 10... Settler tube, 10a... Branch, 11... Bumpful plate, 15... Interface.

Claims (1)

[Claims] 1 Sewage is stored in a sludge zone and a bubbler zone that are formed adjacent to each other in the tank body, and oxygen is added to the liquid by blowing oxygen-containing gas in the bubbler zone into the liquid drawn from the bottom of the sludge zone. The oxygen-dissolved liquid is introduced to the bottom of the sludge zone at a position farthest from the bubbler zone, thereby forming a liquid swirl flow within the sludge zone, and A sewage treatment method characterized by separating a supernatant liquid above the sludge and overflowing the supernatant liquid at a flow rate commensurate with the flow rate of inflow sewage introduced into the tank body.