JPS60261594A - Vertical-shaft surface aerator - Google Patents

Abstract

PURPOSE:To enable aeration and agitation or only agitation by providing an impeller for scraping up water and an agitation impeller to an aerator, and making the aerator rotatable in the normal and the reverse direction. CONSTITUTION:An impeller 3 for scraping up water and an agitation impeller 15 are furnished to an aerator 14, and the agitator is made rotatable in the normal and the reverse direction. With said aerator, aeration and agitation are carried out when the aeration is needed, and only agitation can be carried out when the aeration is not needed or when the agitation is needed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement of a vertical axis type surface aerator used in an aeration tank of an apparatus for biologically treating organic wastewater.

<Prior art> A vertical axis type surface aerator (hereinafter simply referred to as aerator 1) is installed in an aeration tank of a biological treatment device, etc., and its shape is, for example, an inverted truncated cone as shown in FIG. A large number of water scraping blades 3 are inclinedly attached to the lower surface of 2, and the inverted truncated conical body 2 is connected to an electric motor 6 via a reduction gear 5 by a shaft 4, and the inverted truncated conical body 2 is attached near the water surface. It is provided in the following. The aerator 1 rotates an inverted truncated cone body 2 by starting an electric motor 6, and uses inclined water scraping blades 3 to scrape up a large amount of ice and throw it into the air and scatter it on the water surface for aeration. 3, an upward flow occurs in the lower part of the inverted truncated cone 2, and on the other hand, as the water scraping wing 3 scatters the ice around the periphery, a downward flow occurs in areas other than the upper part of the inverted truncated cone 2. This causes a vertical circulation flow to occur in the aeration tank 7, stirring and mixing the inside of the aeration tank 7.

By the way, when organic wastewater (water to be treated) is aerated in an aeration tank 7 equipped with an aerator 1 as shown in FIG. For this purpose, a dissolved oxygen concentration meter 8 has been installed in the aeration tank 7, and the rotation speed of the aerator 1 is controlled based on the measured value to keep the dissolved oxygen concentration in the aeration tank 7 constant. There is. However, since the aerator 1 is designed based on annual average water quality data, it is extremely difficult to design an aerator 1 that can operate efficiently over all daily and seasonal variations. Therefore, when the BOD of the water to be treated is low or the water temperature is low, that is, when the oxygen demand of the water to be treated decreases, in order to achieve the optimal aeration amount (oxygen supply amount), it is necessary to
However, if the oxygen demand is extremely low, it is necessary to lower the rotation speed of the aerator 1 (the minimum circulation flow rate of the tank in which activated sludge is suspended, generally 15 cm).
Even at rotational speeds that are said to be 1/sec), the amount of oxygen supplied may still be excessive. However, if the rotation speed of the aerator 1 is: 1 or more, then T b
yo&B! Inside SO tank 7. Due to the circulation flow rate, -C1 activated sludge is deposited at the bottom of the aeration tank 7. As a solution to this problem, a method is used in which the aerator 1 is operated intermittently and the activated sludge floats and settles repeatedly. However, if the repetition interval is too short, over-aeration will occur and the activated sludge will self-decompose, becoming finer and causing sedimentation. On the other hand, if the interval is too long, the accumulated activated sludge will be compressed, requiring a large flow rate for resuspension, and at the same time prolonging the stirring time, which will complicate operation management. There is.

In addition, when treating water containing ammonia nitrogen and/or organic nitrogen by the so-called four-part activated sludge method, in which the roles of an aeration tank, denitrification rosewood, and sedimentation tank are performed in one tank, As shown in the figure, first, water to be treated is flowed into a tank 9 having a solid portion after solid-liquid separation, that is, concentrated activated sludge at the bottom, through an inflow pipe 10 to form a sludge mixture, which will be described later. conduct. Next, the aerator 1 is started to perform aeration to oxidize BOD in the water to be treated, and at the same time nitrify ammonia nitrogen and/or organic nitrogen to nitrite nitrogen and nitrate nitrogen through the action of nitrifying bacteria. I do. Next, the aerator 1 is stopped and the sludge mixture is stirred by a separately provided stirrer 11 to bring it into an anaerobic state where dissolved oxygen is almost zero, and the nitrified nitrite nitrogen and nitrate nitrogen are removed by the action of denitrifying bacteria. A denitrification step is performed in which ammonia nitrogen and/or organic nitrogen is removed from the water to be treated by reducing it to nitrogen gas and releasing it into the air. Note that since a hydrogen donor (organic substance) is required in the denitrification step, raw water (water to be treated) or methanol or the like is usually added. Next, the aerator 1 is started again to carry out a re-aeration step in which the remaining bone is oxidized using raw water or methanol added as a hydrogen donor. Next, the aerator 1 is stopped and a solid-liquid separation process is performed to separate treated water and activated sludge into solid-liquid. Next, a discharge step is performed in which the liquid portion, that is, the clear water, is taken out of the system through the outflow pipe 12 as treated water. On the other hand, the intermediate portion, that is, the concentrated activated sludge, remains as it is at the bottom of the tank 9, and as described above, new water to be treated flows in and is used for the next cycle of treatment. In addition, the surplus activated sludge of the concentrated activated sludge is removed from the sludge pipe 1 as needed.
3 to the outside of the system. In this way, the four-section activated sludge method performs all treatment in one tank 9, and has the advantage that the treatment equipment is simple, so construction costs are low, and maintenance is easy. When performing nitrification and denitrification, a drawback is that stirring means such as the stirrer 11 must be provided separately from the aerator 1.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned drawbacks.When aeration is necessary, aeration and stirring are performed, and when aeration is unnecessary or when stirring is necessary, aeration and stirring are performed. The object of this invention is to provide an aerator that can perform only stirring.

<Means for Solving the Problems> The present invention provides an aerator that performs aeration by throwing ice blocks into the air and scattering them on the water surface using water scraping blades, and in addition to the water scraping blades, a stirring blade is provided in the aerator. The present invention relates to an aerator that is capable of operating in forward and reverse directions.

The present invention will be explained below based on the drawings.

FIG. 1 is a perspective explanatory view showing an example of an embodiment of the apparatus of the present invention. The aerator of the device of the present invention (hereinafter referred to as special air rake 14) has a shaft 4 connected to the inverted truncated conical body 2 having the water scraping blades 3 of the conventional aerator 1, and the shaft 4 is connected to, for example, a single letter-shaped stirring blade. 15 attached,
It is characterized by being capable of forward and reverse rotation operation. The stirring blade 15 may be of a cross shape, a turbine shape, a propeller shape, etc. in addition to the single shape shape. Further, as another embodiment of the stirring blade 15, as shown in FIG. 2, the stirring blade 15 is rotatably locked by a hinge 16,
When the special aerator 14 is running in the normal direction, the stirring blades 15 become almost horizontal due to the resistance of the water, with almost no resistance to water, and when the special aerator 14 is running in the reverse direction, the stirring blades 15 rotate by their own weight and become almost vertical. Like stopper 1, . The stirring blade 15 is supported by 1 7 and is approximately vertical.
Pushing the water away creates a water flow that stirs the water. In addition to what is shown in Figure 2, there are
As shown in the figure, it is also possible to use a damper type structure in which one end of several stirring blades 15 is rotatably locked by a pin 18, and the damper type is opened during forward rotation and closed during reverse rotation.

<Operation of the Invention> Processing in the aeration tank 7 in which the special aerator 14 of the apparatus of the present invention is installed is performed as follows.

For example, as shown in Fig. 4, the water to be treated flows into the aeration tank 7 through the inflow pipe 10, and the special aerator 14 is operated in normal rotation, and the ice cubes are swept up by the water scraping blades 3 and thrown into the air to be scattered on the water surface. At the same time, a circulating flow is generated in the aeration tank 7, and BOD is removed by the action of activated sludge. Note that the rotation speed of the special aerator 14 is controlled by the signal from the dissolved oxygen concentration meter 8, and processing is performed while maintaining the dissolved oxygen concentration at an appropriate value. The rotation speed control of the special aerator 14 is performed, for example, as follows. In other words, when the setting range of dissolved oxygen concentration is 1.0 to 1.5■0/1, if the detected value of the dissolved oxygen concentration meter 8 is 1.0■0/Il or less, the rotation speed of the special aerator 14 is changed. If the detected value of the dissolved oxygen concentration meter 8 is 1.5■0/1 or more, the rotation speed of the special aerator 14 is lowered to decrease the aeration amount, and the dissolved oxygen concentration meter 8 is increased. Detected value is 1.0 to 1
．． If it is between 5■O/J, control is performed such that the rotation speed of the special aerator 14 is left as it is. Such control allows efficient BOD removal. However, when the BOD of the water to be treated is low, or when the amount of water to be treated is small, that is, when the oxygen demand of the water to be treated is low, the rotation speed of the special aerator 14 may be changed.
Even if the rotation speed is reduced to the minimum that allows the activated sludge in the aeration tank 7 to float, the dissolved oxygen concentration may still be higher than the appropriate value. In such a case, after stopping the special aerator 14, the reverse operation is immediately performed. When the special aerator 14 is operated in reverse, since the water scraping blades 3 are attached to the inverted truncated cone body 2 at an angle, a force acts in the direction of pushing the water against the bottom of the aeration tank 7, and the ice blocks are not scraped up, resulting in an aeration effect. will disappear. However, the inside of the aeration tank 7 can be agitated by a stirring blade 15 of a straight shape, a cross shape, a turbine shape, a propeller shape, etc. attached to the lower part of the inverted truncated cone 2. Due to this operation of only stirring without aeration, the dissolved oxygen concentration gradually decreases and finally reaches the lower limit value (1.0×0/1 in this example). When the lower limit value is reached, the special aerator 14 is stopped and the special aerator 14 is turned on again.
The above operation is repeated with normal rotation operation. In addition, stirring blade 1
5, if a rotatably locked agitating blade 15 as shown in FIGS. 2 and 3 is used, during reverse operation, the agitating blade 15 moves in the direction where there is resistance to water, that is, pushes the water away. As mentioned above, the aeration tank 7 can be stirred in the aeration tank 7. On the other hand, during forward rotation, the agitation blades 15 are in a direction where they receive almost no water resistance. Single character type (Figure 1), cross type,
It is more desirable because it can save power compared to turbine type, propeller type, etc.

In addition, when the special aerator 14 of the present invention is applied to a batch activated 7η mud processing apparatus, there is no need to separately provide a stirring means such as an agitator in addition to the aerator, as explained in the "Prior Art" section. . That is, as shown in FIG. 5, after the water to be treated flows into a tank 9 having concentrated activated sludge at the bottom to form a sludge mixture, the special aerator 14
Start up and perform aeration. In the aeration process, the special aerator 14 is operated in normal rotation, and the water scraping blades 3 scrape up ice blocks and throw them into the air, scattering them on the water surface for aeration, and circulating and stirring the tank 9 to oxidize BOD in the water to be treated. At the same time, ammonia nitrogen and/or organic nitrogen is nitrified by the action of nitrifying bacteria to become nitrite nitrogen and nitrate nitrogen. Next, the special aerator 14 is stopped, and this time the special aerator 14 is operated in reverse to perform the denitrification process. When the special aerator 4 is operated in reverse, the aeration effect disappears as described above, and only the stirring action by the stirring blades 15 works, making it possible to create an anaerobic state in which the dissolved oxygen in the tank 9 is almost zero, and the nitrification occurs. Nitrite nitrogen, nitric acid Nitrite nitrogen is reduced by the action of denitrifying bacteria, converted into nitrogen gas, and released into the air to remove ammonia nitrogen and/or organic nitrogen from the water to be treated. Note that in the aeration step, a hydrogen donor (organic substance) is added as described above. Next, a re-aeration step, a solid-liquid separation step, and a discharge step are performed, but since they are the same as in the batch activated sludge method of the above-mentioned "prior art", their explanation will be omitted.

<Effects of the Invention> As explained above, according to the special aerator of the device of the present invention, even when the oxygen demand of the water to be treated decreases, the stirring power in the aeration tank will not be insufficient, so activated sludge Since the activated sludge does not settle at the bottom of the aeration tank and there is no over-aeration, there is no disassembly due to self-decomposition of the activated sludge, the activated sludge has good settling properties, requires less power consumption, and can be processed using the batch activated sludge method. If the special aerator of the device of the present invention is applied to treat water containing nitrogen in the device,
Since one special aerator functions as an aerator and an agitator, both aerobic and anaerobic conditions can be created, and the cost of machinery and equipment can be kept low.

[Brief explanation of drawings]

1 to 5 all relate to the vertical shaft type surface aerator of the present invention, FIG. 1 is a perspective explanatory view showing an example of an embodiment of the vertical shaft type surface aerator, and FIG. 2 is a vertical shaft type surface aerator. FIG. 3 is a longitudinal cross-sectional explanatory view showing an example of another embodiment of the stirring blade portion of the aerator, FIG. Fig. 5 is a flow explanatory diagram showing an aeration tank to which the device of the present invention is applied, and Fig. 5 is a process explanatory diagram of a batch type activated sludge device to which the device of the present invention is applied. Regarding the axial type surface aerator, Fig. 6 is a vertical cross-sectional explanatory diagram showing an example of a vertical axial type surface aerator, Fig. 7 is a flow explanatory diagram showing an aeration tank to which the vertical axial type surface aerator is applied, and Fig. 8 is a It is a process explanatory diagram of a batch type activated sludge system to which a vertical axis type surface aerator is applied. 1... Vertical shaft type surface aerator (aerator) 2...
Inverted truncated cone 3... Water scraping blade 3 4... Shaft 5... Reducer 6... Electric motor 7... Aeration tank 8... Dissolved oxygen concentration meter 9... Tank 10. ... Inflow pipe 11 ... Stirrer 12 ... Outflow pipe 13 ... Sludge removal pipe 14 ... Special air rake 15 ... Stirring blade 16 ...
・Hinge 17...Stopper 18...Pin 4 Fig. 1 Fig. 3 Fig. 2 Reverse private burial private dark trunk return 621- 3 Risanshin Yukanchua Nissakuoka ○ ＼- Fig. 4 B Figure 5 0 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A vertical shaft type surface aerator that performs aeration by throwing ice blocks into the air and scattering them on the water surface using double blades, is provided with stirring blades in addition to the water scraping blades, and the vertical shaft A vertical axis type surface aerator characterized in that the mold surface aerator is provided so as to be capable of forward and reverse rotation operation. 2. Claims characterized in that the vertical shaft type surface aerator rotatably locks the stirring blade so that there is no resistance to water during normal rotation operation, and there is resistance to water during reverse rotation operation. Vertical axis type surface aerator according to item 1.