JPS6136478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sewage purification apparatus for converting sewage into an activated sludge treatment liquid by performing aeration using oxygen gas.

In activated sludge treatment of wastewater, the supply of oxygen necessary for the activity of microorganisms involved in biological oxidation reactions is generally carried out by blowing air into the wastewater contained in an aeration tank. However, in order to supply oxygen even more efficiently, it is also possible to use a gas containing a higher proportion of oxygen than air (hereinafter referred to as "high concentration oxygen gas" or simply "oxygen gas"). ing. When using high-concentration oxygen gas, the efficiency with which oxygen is absorbed into the water to be treated increases as the time that the oxygen gas is in contact with the water to be treated increases, provided that other conditions remain the same. Generally, in order to recover oxygen gas that is not absorbed by the water, oxygen gas is injected using a diffuser installed at a predetermined depth from the water surface inside a cylinder with a closed top. Therefore, the oxygen absorption efficiency depends on the depth of the diffuser. If the BOD of the inflowing sewage is high, the water depth of the reaction tank will become deeper due to the volume load, so it is possible to make the water depth of the aerator deeper. However, if the BOD of the inflowing sewage is low, the reaction tank will become deeper. Although the water depth of the tank can be shallow, it is necessary to make the water depth of the diffuser deeper than the water depth of the reaction tank to increase oxygen absorption efficiency. This type of purification device is unnatural, so either the depth of the diffuser is made shallow at the expense of oxygen absorption efficiency, or the depth of the reactor is made deeper than necessary, ignoring proper volume loading. be forced to suffer inconveniences such as

This invention makes it possible to install an aeration diffuser that blows oxygen gas into water at a predetermined water depth regardless of the water depth of the reaction tank, thereby achieving extremely good oxygen dissolution efficiency even when the BOD of inflow sewage is low. The object of the present invention is to provide a sewage purification device that can achieve the above goals.

Next, an embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 in the figure indicates one of a plurality of reaction vessels made of concrete or the like, and within this reaction vessel 1, one or more circulation devices 2 are installed.

The circulation device 2 includes a cylindrical settler inner cylinder 3 that stands vertically from the bottom of the reaction tank 1, and this settler inner cylinder 3.
It has a settler ring 4 coaxially arranged on the outside of the settler inner cylinder 3, and a bubbler pipe 5 coaxially arranged inside the settler inner cylinder 3. Setra inner cylinder 3
The settling ring 4 can have any cross-sectional shape such as a circle or a polygon depending on the planar shape of the reaction tank 1 and the number and arrangement pattern of the circulation devices 2 provided therein. The bubbler pipe 5 is selected to have the same cross-sectional shape as the settler inner cylinder 3. In this example, the setter inner cylinder 3 is made of concrete, but it can be made of any material such as synthetic resin.

The settler ring 4 is made of corrosion-resistant material such as stainless steel or vinyl chloride resin, and its upper end is airtightly closed by a cover plate 6, and its lower end is closed along an inclined surface formed at the lower end of the outer surface of the settler inner cylinder 3. An extending inclined surface 4a is formed. The inner diameter of the settler ring 4 is larger than the outer diameter of the inner settler cylinder 3, so that an annular passage 7 is formed between the two. Note that the reference numeral 19 indicates a support for supporting the settling ring 4 in a predetermined position.

Further, the bubbler tube 5 has a diameter capable of forming an annular passage 8 between it and the inner surface of the settler inner cylinder 3, its lower end is in contact with the bottom surface of the reaction tank 1, and its upper end is in contact with the inner surface of the settler inner cylinder 3.
It reaches a position slightly higher than the top of the . Furthermore, a passage 8 on the outside of the lower end of the bubbler tube 5 is provided.
A plurality of bubbler openings 9 are formed to communicate with the inside, and the upper end reaches a height approximately equal to the liquid level WL in the reaction tank 1. This liquid level WL is determined by the height of the upper edges of two overflow troughs 10 that touch the outer circumferential surface of the settler ring 4 and extend in the tangential direction. It extends outside the reaction vessel 1 for discharge. Further, a ring 11 that reaches from the outer peripheral surface of the bubbler tube 5 to the upper end of the settler inner cylinder 3 closes the upper end of the passage 8.

An oxygen gas supply pipe 12 connected to an oxygen gas supply mechanism (not shown) passes through the lid plate 6, extends to the bottom of the bubbler pipe, and supplies high concentration oxygen gas to a diffuser 13 attached to its tip.

On the other hand, the upper edge of the annular sludge suction trough 14 provided along the outer peripheral surface of the settler ring 4 is a sludge level formed in the reaction tank 1 under normal operating conditions.
It is set at approximately the same height as SL, and its interior communicates with the passage 8 through the settler ring 4 and the settler inner cylinder 3. The passage 8 has an open end of a waste water supply pipe 15 for introducing waste water to be treated.

The reference numeral 16 indicates a settling ring 4 and a bubbler tube 5.
and a gas-liquid separation zone formed by the ring 11; 17 is an annular buttful provided in the gas-liquid separation zone 16; 18 is a discharge pipe for discharging the separated gas onto the liquid surface in the settler ring 4; Each is shown below.

In the sewage purification apparatus configured as described above, when high-concentration oxygen gas is sucked from the oxygen gas supply pipe 12 through the diffuser 13 into the liquid in the bubbler pipe 5, this liquid is affected by the upwelling force of the gas. Therefore, it rises inside the bubbler pipe 5, and along with this, the waste water supply pipe 15
A liquid containing sewage supplied from the suction trough 14 and sludge sucked from the suction trough 14 flows into the bubbler pipe 5 through the passage 8 and the bubbler opening 9.

While the liquid rises in the bubbler tube 5 with bubbles of high concentration oxygen gas, it absorbs oxygen gas, overflows the upper end of the bubbler tube 5, flows into the gas-liquid separation zone 16, and is not absorbed. After the gas is separated from the liquid, it is discharged from the discharge pipe 18 and reused as necessary. In the gas-liquid separation zone 16, during residence for a predetermined time, absorption of mixed oxygen in the form of fine bubbles and separation of bubbles remaining without being absorbed are performed, and therefore the gas-liquid separation zone 16 contains a large amount of oxygen.
A liquid containing almost no air bubbles flows into the bottom of the reaction vessel 1 through the passage 7. As shown in the figure, the bottom outer circumferential surface of the settler inner cylinder 3 is inclined so as to approach the opposing side surfaces sequentially as it goes downward, so that the liquid flowing down along this outer circumferential surface is
The oxygen is guided by the inclined surface and evenly distributed at the bottom of the reaction tank 1, supplying a sufficient amount of oxygen to the liquid in the reaction tank 1. In the above embodiment, the bottoms of the settler inner cylinder 3 and bubbler pipe 5 and the bottom of the reaction tank 1 are at the same level, but the former can be made deeper than the latter depending on the BOD concentration of the inflowing sewage. , the same effect can be obtained in this case as well.

The liquid that has absorbed a large amount of oxygen in the circulation device 2 is
Since it flows quietly into the reaction tank 1 and contains almost no air bubbles, the liquid in the reaction tank 1 is kept almost completely stationary, and the sludge naturally settles to reach the sludge level SL. Form.
Then, this liquid is sucked into the passage 8 from the suction trough 14 that opens near the sludge level SL,
After absorbing oxygen again in the above order, it returns to the reaction tank 1 and is biologically purified during this circulation process.
The liquid that has undergone a predetermined purification process is then taken out to the outside via the overflow trough 10 at a flow rate commensurate with the amount of new wastewater flowing in. Since the liquid taken out from the overflow trough 10 is clear and separated above the sludge level SW, there is no need to perform any treatment to separate the activated sludge.

As described above, according to the present invention, while the liquid is quietly circulated between the reaction tank and the circulation device, the oxygen necessary for the biological purification effect performed in the reaction tank can be effectively supplied. I can do it. Moreover, in the circulation device, the liquid in the bubbler tube absorbs oxygen while rising together with the bubbles of high-concentration oxygen gas blown into it, and a gas-liquid separation zone is formed outside the upper end of the bubbler tube. During the residence time, more oxygen is absorbed and air bubbles are separated. Therefore, there is no need to make the length of the bubbler tube (depth from the liquid surface) longer than necessary.
The effect is that the depth of the reaction tank can be set to a value suitable for a predetermined volumetric load.

[Brief explanation of the drawing]

The figure is a schematic vertical sectional view of a sewage purification apparatus according to an embodiment of the present invention. 1...Reaction tank, 2...Circulation device, 3...Settler inner cylinder,
4... Settling ring, 5... Bubbler pipe, 7, 8... Passage, 9... Bubbler opening, 10... Overflow trough, 12...
Oxygen gas supply pipe, 13... Diffuser, 14... Sludge trough, 15... Sewage supply pipe, 17... Batsuful, 18...
Exhaust pipe.

Claims (1)

[Claims] 1 Consists of a reaction tank equipped with an overflow trough for taking out treated water from a position close to the liquid level, and one or more circulation devices installed inside this reaction tank, each circulation device having the above-mentioned A settler inner cylinder vertically installed from the bottom of the reaction tank, a bubbler pipe inserted coaxially into the settler inner cylinder and forming a first passage between the settler inner cylinder, and a bubbler pipe inside the settler. a settler ring that is installed outside the cylinder, is arranged to form a second passage between the settler inner cylinder and has a closed upper end; a gas-liquid separation zone for receiving the liquid overflowing from the upper end of the bubbler tube and sending it to the reaction tank via the second passage after residence for a predetermined time; It has a sludge suction trough that sucks liquid into the first passageway from near the sludge level formed in the reaction tank, and a sewage supply pipe that supplies wastewater to be treated to the first passageway. A sewage purification device featuring: