JPH0239960B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a stirring aeration device that is capable of adjusting the discharge flow rate of sewage mixed with air bubbles.

(Prior art) The stirring aeration equipment used in the activated sludge treatment method, which is generally used for conventional sewage treatment, is equipped with an aeration pipe at the bottom of the aeration tank. It is configured to erupt. This configuration is widely used because it has a simple structure and can be constructed at low equipment cost. However, the air diffuser pipes are easily clogged, and the fine air bubbles released from the air diffuser pipes become large lumps during the floating process and drift, resulting in insufficient mixing of wastewater and air, making it difficult to obtain a sufficient aeration effect. I had a problem where I couldn't do it.

Furthermore, in order to avoid performance deterioration due to the bulking phenomenon peculiar to the activated sludge treatment method, various sewage treatment devices of the submerged filter bed type, which is a type of biofilm method, have been proposed. In this immersed filter bed type sewage treatment equipment, a filter bed body made of a honeycomb core or a net ring is immersed in wastewater, and a vertical pipe installed in the center of the filter bed body is used as a circulation flow path. The wastewater is circulated through the filter bed several times for treatment. The technology for stirring aeration equipment that mixes and circulates air in wastewater was developed by Jikosho.
As shown in No. 62-18320, compressed air is sent to the bottom of the vertical pipe to create an upward flow within the vertical pipe as an air lift pump, and the air and wastewater come into contact with each other in the process of rising within the vertical pipe. . Also, as shown in Utility Model No. 56-1439,
Some pumps rotate a vertical shaft axial flow pump with a part of its impeller immersed in the dirty water surface above the vertical pipe, drawing in air and creating a downward flow of a gas-liquid mixture into the vertical pipe. Furthermore, as shown in Utility Model Publication No. 58-26077, a vertical shaft axial flow pump is installed in a vertical pipe, and an air pipe communicating with outside air is opened near the suction side of this vertical shaft axial flow pump. Some pumps use negative pressure generated by the rotation of an axial flow pump to suck in air and circulate wastewater while also mixing air into the wastewater.

(Problems to be Solved by the Invention) By the way, in submerged filter bed type sewage treatment equipment, the higher the discharge flow rate of the stirring aeration device and the faster the circulating flow rate, the more the sewage comes into contact with the filter bed body, and the treatment performance becomes worse. performance in the spring season is improved compared to the winter season.
This is illustrated by the experimental data in FIGS. 5 and 6. Figure 5 is a characteristic diagram of the relationship between the circulation flow rate in the filter bed and the ammonia nitrogen removal rate in winter (January) when the water volume load was changed.
The figure is a characteristic diagram for the spring season (May).

As is clear from Figures 5 and 6, in winter, the higher the circulation flow rate, the higher the ammonia nitrogen removal rate, but in spring, when the circulation flow rate exceeds a certain value, ammonia nitrogen removal rate increases. The nitrogen removal rate does not increase with circulation flow rate. Furthermore, the processing performance in spring is superior to that in winter.

Here, in order to most economically maintain constant good treatment performance throughout the year, the discharge flow rate of the stirring aerator should be increased in the winter to increase the circulation flow rate, and in the spring the discharge flow rate should be lower than in the winter. It is desirable to reduce the circulation flow rate.

However, the stirring aeration device in the conventional submerged filter bed type sewage treatment equipment has the following problems. First, when circulating using an air lift pump that sends compressed air to the bottom of a vertical pipe, it is not possible to increase the circulation speed in the vertical pipe beyond the floating speed of bubbles, and the power cost is high because it sends a large amount of air. Bulk, sagging, and large bubbles prevent sufficient contact and mixing of wastewater and air, making it impossible to obtain a sufficient aeration effect. In addition, for those that use a vertical shaft axial flow pump, it is possible to adjust the circulating flow speed in the vertical pipe by adjusting the pump rotation speed, but it requires a speed conversion means etc. to adjust the rotation speed. , the equipment cost increases accordingly.

The object of the present invention was made to solve the problems of the conventional stirring aeration apparatus described above, and it is an object of the present invention to provide a stirring aeration apparatus that can arbitrarily adjust the discharge flow rate of sewage mixed with air bubbles.

(Means for Solving the Problem) In order to achieve the above object, the stirring aeration device of the present invention has a substantially truncated flow path that widens toward the discharge side of a vertical shaft axial flow pump housed in an outer casing. A conical discharge cone is provided, and an annular slide gate for adjusting the opening area of the divergent flow path is disposed at the discharge side end of the outer body casing so as to be freely slidable in the axial direction. A ventilate part forming a narrow part in the outer peripheral flow path is provided on the slide gate, and a diffuser hole communicating with the gas supply means is opened at a position facing the throat part of the ventilium part or the throat part of the discharge cone. It is configured.

(Function) The discharge flow rate can be adjusted by adjusting the opening area of the divergent channel provided on the discharge side of the vertical axial flow pump by sliding the slide gate. In addition, since the slide gate is provided with a ventilate portion and a narrow portion is formed on the outer periphery of the discharge cone, air bubbles are attracted and mixed into the waste water by the negative pressure generated by the high-speed flow of waste water passing through this narrow portion.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a longitudinal sectional view of one embodiment of the stirring aeration device of the present invention, FIG. 2 is a diagram showing an example of the adjustment mechanism of the slide gate of FIG. 1, and FIG. FIG. 3 is a characteristic diagram of discharge flow rate by adjusting a gate.

In FIGS. 1 and 2, an axial flow impeller 2 rotationally driven by an underwater motor 1 is installed inside an outer casing 3 supported by ribs 4, 4, . . . to constitute a vertical axial flow pump 5. . The suction side end of the outer body casing 3 opens outward in a bell shape to form a suction port 6. Further, on the discharge side of the vertical shaft axial flow pump 5, a discharge cone 7 having a substantially truncated cone shape is provided, and the discharge side end of the discharge cone 7 opens outward in a bell shape to allow a widening flow at the end. A path is formed.
The discharge cone 7 is fixed to the legs 9 by fixed stands 8, 8, . The outer casing 3 is supported and fixed to the discharge cone 7 by radial ribs 10, 10, . . . . Further, an annular slide gate 11 is disposed at the discharge side end of the outer casing 3 so as to be slidable in the axial direction. The slide gate 11 includes an annular slide portion 11a that is loosely fitted around the outer periphery of the discharge side end of the outer body casing 3 to form a ventilate portion with the discharge cone 7, and a nozzle portion whose diameter is gradually reduced. 11b, a throat portion 11c forming a narrow portion with the outer periphery of the discharge cone 7;
Continuing from this throat portion 11c, a diffuser portion 11d in the shape of an enlarged conical tube whose diameter gradually increases.
It consists of And the differential user part 1
A discharge port 12 is formed by the end of the slide gate 1 d, that is, the discharge side end of the slide gate 11 and the discharge side end of the discharge cone 7 . Furthermore, a mirror plate 13 is provided on the discharge cone 7 to form a hollow chamber 14, and the hollow chamber 14 is communicated with the slide gate 11.
A large number of small-diameter air diffusion holes 15, 15, . . . are bored in the discharge cone 7 facing the throat portion 11c.
One end of an air pipe 16 is opened into the hollow chamber 14, and the other end of the air pipe 16 is opened to the atmosphere via an on-off valve 17.

Further, the opening/closing mechanism of the slide gate 11 includes a swing arm 19 swingably disposed on a fulcrum 18 provided on the outer periphery of the outer casing 3, and one end connected to the slide gate 11 via an operating rod 20.
The other end is connected via a drive rod 21 to an electric device 22 and a manual device 23 placed on a frame above the aeration tank.

In such a configuration, if the slide gate 11 is adjusted to the upper position as shown by the two-dot chain line in FIG. The number increases as follows. Further, if the slide gate 11 is adjusted to the lower position as shown by the solid line in FIG. 1, the opening area of the flow path of the discharge port 12 becomes narrower, and the discharge flow rate decreases as shown by the broken line in FIG. 3.

And the throat part 11c of the bench lily part
Since the flow path is narrowed to form a narrow portion, the wastewater passes through the throat portion 11c at a high speed. Therefore, due to the load caused by this high-speed flow, air bubbles are sucked into the wastewater from the air diffusion holes 15, 15, . . . .

By the way, as shown in Figure 1, slide gate 1
1 upward to widen the opening area of the flow path of the discharge port 12, the throat portion 11 is moved so that the flow path facing the air diffuser holes 15, 15...
If c is a conical shape slightly expanding downward in Fig. 1, the throat portion 11c
The flow rate of wastewater passing through becomes constant, and the amount of suction of air bubbles becomes almost constant.

Therefore, even if the slide gate 11 is adjusted, the suction amount of bubbles does not change, and only the discharge flow rate is adjusted appropriately.

FIG. 4 is a partial vertical cross-sectional view showing a slide gate of another embodiment of the stirring aeration apparatus of the present invention. In FIG. 4, the same members as those in FIG. 1 are given the same reference numerals and redundant explanations will be omitted.

The differences in Figure 4 from Figure 1 are as follows:
The throat portion 11c' of the slide gate 11' has a conical shape that expands slightly upward, and when the opening area of the flow path of the discharge port 12 is expanded, the flow path of the throat portion 11c' becomes slightly narrower, and when the opening area is narrowed, the throat The reason is that the flow path in the portion 11c' is made slightly wider.

In such a configuration, the slide gate 11'
When the discharge flow rate is increased by setting the drain to the upper position, the waste water passes through the throat portion 11c' at a higher speed, and a large amount of air bubbles are sucked into the throat portion 11c'. Also, slide gate 1
1' to reduce the discharge flow rate, the waste water passes through the throat portion 11c' at a lower speed, and the suction of air bubbles is reduced.

As described above, the change in the opening area of the flow path facing the air diffuser holes 15, 15, . . . due to the vertical movement of the slide gates 11, 11' is appropriately set in advance. In other words, the throat portion 11c
If the flow rate of wastewater is kept constant,
The amount of air bubbles that are sucked and mixed becomes constant. Furthermore, if the flow rate of the waste water flowing through the throat portion 11c' is made higher with respect to the increase in the discharge flow rate, the amount of air bubbles that are sucked and mixed in is increased. Furthermore, if the flow rate of wastewater is made lower than the discharge flow rate, the amount of air bubbles that are sucked in is reduced. Therefore,
The relationship between the discharge flow rate and the amount of air bubbles to be sucked and mixed can be set in advance as appropriate.

Note that the above embodiment has been described when the on-off valve 17, which has an air pipe 16 interposed therebetween, is in the fully open state. Of course, it can be adjusted. Furthermore, by fully closing the on-off valve 17, wastewater can be discharged without suctioning and mixing of air bubbles. Therefore, the stirring aeration device of the present invention can also be used as an underwater stirring device that can be used as a partner for the anaerobic treatment step using low-speed stirring and the aerobic treatment step using high-speed stirring aeration in the batch activated sludge treatment method. Further, in the above embodiment, the slide gates 11 and 11' are themselves formed of a ventilate part, but a ventilary tube may be provided on the inner wall of the slide gate, and the slide gate and the ventilic tube are formed. One end of the air pipe 16 may be appropriately opened in the hollow chamber, and an air diffuser hole may be bored in the throat portion of the ventilate pipe.

Furthermore, in order to aerate oxygen-deficient areas such as lakes and marshes, the stirring aeration device of the present invention may be appropriately disposed diagonally or horizontally in water in oxygen-deficient areas.

(Effects of the Invention) As explained above, according to the stirring aeration device of the present invention, the discharge flow rate can be adjusted as appropriate by adjusting the slide gate. In addition, an excellent effect can be achieved in that the amount of bubbles sucked and mixed can be designed to have an appropriate relationship with the discharge flow rate.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the stirring aeration device of the present invention, FIG. 2 is a diagram showing an example of the adjustment mechanism of the slide gate of FIG. 1, and FIG. FIG. 4 is a partial vertical cross-sectional view showing a slide gate of another embodiment of the stirring aeration device of the present invention, and FIG. 5 is a characteristic diagram of discharge flow rate depending on gate adjustment. FIG. 6 is a characteristic diagram of the relationship between the circulation flow rate in the filter bed and the ammonia nitrogen removal rate when the water volume load is changed in an experiment.
The figure is a characteristic diagram for the spring season (May). 3: Outer body casing, 4: Rib, 5: Vertical axial flow pump, 7: Discharge cone, 11, 11': Slide gate, 11c, 11c': Throat part, 1
2: Discharge port, 14: Hollow chamber, 15: Diffusion hole, 1
6: Air pipe.

Claims (1)

[Scope of Claims] 1. A generally truncated cone-shaped discharge cone forming a divergent flow path is provided on the discharge side of a vertical shaft axial flow pump housed in an outer casing, and a discharge cone having a generally truncated conical shape forming a flow path that widens toward the end is provided at the discharge side end of the outer casing. An annular slide gate that adjusts the opening area of the divergent flow channel is disposed to be slidable in the axial direction, and a ventilate part that forms a narrow part in the flow channel around the outer periphery of the discharge cone is provided on the slide gate. A stirring aeration device, characterized in that an aeration hole communicating with a gas supply means is opened at a throat portion of the ventilate portion or at a position facing the throat portion of the discharge cone. 2. The agitation according to claim 1, wherein when the slide gate is slid in a direction to widen the opening area of the divergent flow path, the flow path facing the aeration hole becomes slightly wider. Aeration equipment. 3. The agitation according to claim 1, characterized in that when the slide gate is slid in a direction to widen the opening area of the divergent channel, the channel facing the aeration hole becomes slightly narrower. Aeration equipment.