JPH03245900A - Revolving flow type deep aeration tank and aeration method - Google Patents

Abstract

PURPOSE:To eliminate the dead zone region on the backside of a baffle plate without lowering of oxygen moving efficiency by also arranging an auxiliary air diffusion device in the vicinity of the backside of the baffle plate. CONSTITUTION:A strong revolving stream is generated in a deep tank body 1 by blowing air into sewage from the air diffusion device 3 set on the single side of the baffle plate 2 provided in the deep tank body, not only to supply dissolved oxygen into sewage but also to mix and stirr activated sludge and a substrate. By also blowing a small amount of air into sewage from the vicinity of the backside of the baffle plate 2 by the auxiliary air diffusion apparatus 4 also arranged in the vicinity of the backside of the baffle plate 2, a also revolving stream can be generated in the center part of the tank body where a dead zone region is formed heretofore. By this method, the mixing properties, treatment capacity and air diffusion efficiency of the whole of the tank body are enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a swirl flow type deep aeration tank and an aeration method used for activated sludge treatment in a sewage treatment plant.

(Prior art) In recent years, aeration tanks in sewage treatment plants have become larger and deeper in order to deal with large volumes of sewage. A method has been adopted in which a baffle plate is provided in the vertical direction to narrow the width of the lower opening between the lower end of the baffle plate and the tank bottom to ensure the required bottom flow velocity.

However, according to the research conducted by the present inventors, a swirling flow as shown in Fig. 6 is formed inside a deep aeration tank having such a baffle plate, but there is a core of the swirling flow on the back side of the baffle plate. There is a region where the flow velocity is extremely low. In this area, there are almost no air bubbles and there is little supply of dissolved oxygen due to the swirling flow, resulting in a dead zone, and this area occupies a large proportion of the entire aeration tank (as a result, treatment performance and aeration efficiency decrease). Although this area can be reduced to some extent by increasing the ventilation rate of the air diffuser, increasing the ventilation rate leads to a significant decrease in diffusion efficiency such as oxygen transfer efficiency and power efficiency. It has also become clear that

(Problems to be Solved by the Invention) The present invention solves the conventional problems as described above, and can eliminate the dead zone area on the back side of the baffle plate without causing a decrease in oxygen transfer efficiency, etc. It was completed to provide a swirl flow type deep aeration tank and an aeration method.

(Means for Solving the Problem) The above problem is solved by a swirling flow type deep aeration tank in which a panful plate is provided vertically inside the deep tank body and an aeration device is arranged in the middle part of one side. This problem can be solved by using a swirl flow type deep aeration tank, which is characterized by having an auxiliary air diffuser installed near the back side of the plate.

In addition, the above problem can be solved by blowing air into the water from a diffuser on one side of the baffle plate installed inside the deep tank body, creating a strong swirling flow in the tank, supplying dissolved oxygen and stirring. This problem can be solved by an aeration method characterized by blowing a small amount of air from near the back side of the baffle plate to generate a gentle swirling flow in the center of the tank.

The present invention will be explained in detail below with reference to the drawings. In Fig. 1, (1) is a deep tank body, (2) is a baffle plate provided vertically inside the tank body, and (3) is a baffle plate on one side of the deep tank body. This is any type of air diffuser such as an air diffuser plate, air diffuser pipe, membrane diffuser, etc. arranged in the middle section. The depth tank body (1) varies depending on the treatment plant, but for boat fishing, it is about 7 to 11 m deep, 7 to 11 m wide, and 4 to 6 m deep with aeration. Moreover, the installation position of the baffle plate (2) is about 1/3 to 172 of the tank width, and the bubbling area of the air diffuser (3) is about 3 to 12% of the tank bottom area.

In the present invention, such a baffle plate (2)
An auxiliary air diffuser (4) is also installed near the back side of the.

Air can be supplied to the auxiliary diffuser (4) by a pipe branched from the riser pipe for supplying air to the diffuser W (3), or by a separate system of pipes. good. The auxiliary air diffuser (4) should be installed near the powerful plate (2) and inside the tank radial 273. Also, it is preferable that the installation water depth is the same as that of the aeration device (3) so that the aeration water pressure is equalized.
The baffle plate (2) may be installed anywhere within the installation range. In this case, it is necessary to use a separate system for air supply piping. The total foaming area of the auxiliary air diffuser (4) is 10 to 30% of the foaming area of the air diffuser (3), and its ventilation strength (aeration amount per unit foaming area) is equal to the ventilation strength of the air diffuser (3). be equal to or less than. Note that the total foaming area of the auxiliary air diffuser (4) is 1 of the foaming area of the air diffuser (3).
If it is less than 0%, the effect of improving oxygen transfer efficiency, etc. will be insufficient, as shown in the data of the later examples, and conversely, if it is less than 30%
If it exceeds this, the original swirling flow caused by the air diffuser (3) will be inhibited, and it will be difficult to secure the required bottom flow velocity.

(Function) The swirl flow type deep aeration tank of the present invention configured as described above has the following features:
A panful plate (
By blowing air into the water from the air diffuser (3) on one side of 2), a strong swirling flow is generated in the tank, supplying dissolved oxygen to the wastewater, and mixing and stirring the activated sludge and substrate. The procedure is the same as in the conventional method.

However, in the present invention, an auxiliary air diffuser (4) is also installed near the back side of the baffle plate (2), and this auxiliary air diffuser (4) also allows a small amount of air to be removed from near the back side of the pan full plate (2). By blowing air into the tank, a gentle swirling flow can be generated as shown in FIG. 1 even in the center of the tank, where a dead zone area was conventionally formed.

This makes it possible to improve the mixability, treatment performance, and aeration efficiency of the entire tank.

Examples of the present invention are shown below.

(Example) An air diffuser and an auxiliary air diffuser having the areas shown in the table below were installed on both sides of the baffle plate of a deep tank for experiments with a water depth of 7 m, a tank width of 8 m, and an aeration depth of 4 m. , BOD removal experiments and aeration performance measurements were conducted under the ventilation conditions shown in the table. For comparison, similar measurements were also performed on a conventional type without an auxiliary diffuser. In addition, the air diffuser and auxiliary air diffuser are 300 x 300 W x 30.
' A porcelain diffuser plate was used.

As a result, as shown in the table, in the swirl flow type deep aeration tank of the present invention, both the oxygen transfer efficiency and the BOD removal rate were improved compared to the conventional ones. In addition, the bubble volume distribution in the aeration tank and the 00 distribution in the aeration tank of Example 1, Example 2, and Comparative Example are shown in Figures 2 to 4. In these figures, Figure A shows the bubble volume distribution. Figure B shows the 00 distribution.

As is clear from FIGS. 2 to 4, according to the present invention, the area where the amount of bubbles is less than 0.05% can be significantly reduced, and at the same time, the area where the amount of bubbles is less than 0.05% can be significantly reduced. It was also possible to significantly reduce the area below lppm.

Furthermore, FIG. 5 shows the oxygen transfer efficiency (○) and the bottom flow velocity at the bottom of the baffle plate when the ratio of the bubbling areas of both diffusers is changed. As can be seen from this figure, the foaming area of the auxiliary air diffuser is 10 times the foaming area of the normal air diffuser.
~20%, the bottom flow velocity is 10 CIl/S
It is possible to improve the oxygen transfer efficiency while maintaining the oxygen transfer efficiency to be equal to or higher than e c.

(Effects of the Invention) As explained above, according to the present invention, by blowing a small amount of air from the vicinity of the back side of the buff full plate to generate a gentle swirling flow in the center of the tank, the back side of the buff full plate is The dead zone area can be eliminated, and the treatment performance and aeration performance of the entire tank can be improved without increasing the ventilation rate. Therefore, the present invention greatly contributes to the development of industry as a swirl flow type deep aeration tank and aeration method that solve the conventional problems.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the present invention, FIG. 2A is a bubble volume distribution diagram in Example 1, FIG. 2B is a DO distribution diagram in Example 1, and FIG. 3A is an implementation example. Bubble amount distribution diagram in Example 2, Figure 3B is Do distribution diagram in Example 2,
Figure 4A is a bubble volume distribution diagram in the comparative example, Figure 4B is a DO distribution diagram in the comparative example, and Figure 5 is the oxygen transfer efficiency and bottom surface when the ratio of bubbling areas of both diffusers is changed. A graph showing changes in flow velocity. FIG. 6 is a schematic cross-sectional view showing a conventional example. (1): Deep tank body, (2): Baffle plate, (3): Air diffuser, (4): Auxiliary air diffuser.

Claims (1)

[Claims] 1. In a swirling flow type deep aeration tank in which a baffle plate (2) is vertically provided inside the deep tank body (1) and an aeration device (3) is arranged in the middle part of one side of the baffle plate (2). , there is also an auxiliary air diffuser (4) near the back side of the baffle plate (2).
A swirl flow type deep aeration tank characterized by being installed with. 2. The foaming area of the auxiliary air diffuser (4) is compared to that of the normal air diffuser (
3. The swirling flow type deep aeration tank according to claim 1, wherein the foaming area is 10 to 30% of the foaming area of step 3). 3. By blowing air into the water from the diffuser (3) on one side of the baffle plate (2) installed inside the deep tank body (1), a strong swirling flow is generated in the tank, and dissolved oxygen is supplied. An aeration method characterized by stirring and stirring, and also blowing a small amount of air from near the back side of the baffle plate (2) to generate a gentle swirling flow in the center of the tank.