JPH09276891A - Deep tank aeration apparatus and operation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently supply air necessary for the removal of BOD, the nitrification of nitrogen and the sedimentation of a carrier or sludge by disposing a first air diffusion device to the middle stage part of one of the cambers of a deep aeration tank having a partition wall formed to the central part thereof and disposing a second air diffusion device to the bottom part of the deep aeration tank. SOLUTION: A first air diffusion device 3a is disposed to the middle stage part of one of the chambers of a revolving flow middle stage aeration type deep aeration tank having a partition wall formed to the central part thereof and performing the removal of BOD in waste water and the nitrification of nitrogen at the same time and a second air diffusion device 5a is attached to the bottom surface of the aeration tank. The air sending amt. of the first air diffusion device 3a is controlled by a first control device 4a and that of the second air diffusion device 5a is controlled by a second control device 6a. By supplying air from these air diffusion devices 3a, 5a, strong revolving streams of flow velocity of 2m/min or more are obtained at the bottom part of the deep aeration tank and, even if a carrier with specific gravity of 1.0-1.1 is used, the sedimentation of the carrier or sludge is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep tank aeration apparatus capable of nitrifying nitrogen at the same time as removing BOD in wastewater such as sewage and organic wastewater, and a method of operating the same.

[0002]

2. Description of the Related Art Conventionally, for example, a standard aeration tank having a water depth of 4 to 5 m is used, and as shown in FIG.
Alternatively, as shown in FIG. 11, sewage,
It has been practiced to treat BOD in wastewater such as organic wastewater. In recent years, because it has become difficult to secure land for treatment plants such as sewage treatment plants in urban areas, for the purpose of removing BOD, for example, the water depth has been doubled or more compared to a standard aeration tank as shown in FIG. Deepening, a middle-stage aeration type deep tank aeration tank with a water depth of 8 to 10 m, which has a partition wall in the center, has come to be installed.

Further, in order to protect the environment, it is necessary to highly treat the wastewater, for example, to remove nitrogen and phosphorus in the wastewater after removing the BOD in the wastewater. Then, nitrogen in the wastewater was nitrified and denitrified by further aeration. For example, in the sewage treatment for removing BOD in sewage, the required oxygen amount of the middle stage aeration type deep aeration tank is BO
When only D is removed, 0.3 per 1 m ^{3 of} deep tank aeration tank
~ 0.5 kgO ₂ / tank m ³ days, but the required oxygen amount when nitrifying nitrogen at the same time as BOD removal is ₂ times this value.
Increase the 2.5 fold 0.6 ~1.2 kgO ₂ / tank m ³ days.
Further, generally, a carrier for supporting microorganisms in the standard aeration tank is added to about 10% of the aeration tank volume to improve the reaction rate, but since the treatment capacity is improved, the required oxygen amount is required. Increases with the amount of carrier. For example,
The carrier is added to the deep aeration tank of the middle aeration type with
%, The required oxygen amount when nitrogen is nitrified at the same time as removal of BOD in sewage is 4 to 5 times that of 1.2 to 2.4 kgO ₂ / tank m ³ days compared to the case of only removal of BOD. Becomes

The increase in the amount of treated water due to the population increase, and the BO
In order to improve the quality of treated water such as D removal and nitrogen removal, it is required to secure the necessary oxygen amount for aeration treatment of wastewater, but as a sewage treatment plant, equipment is required from the aspect of equipment cost and equipment depreciation. Since it is difficult to install all new facilities, in most cases the existing middle-stage aeration type deep tank aeration tank will be used to improve the equipment, and if additional equipment is installed, the necessary oxygen amount for aeration processing will be secured. It is being examined whether it can be done. In the middle aeration type deep aeration tank, if the area occupied by the air diffuser increases, the swirling flow may collide with the air diffuser and a normal swirling flow may not be formed. It was problematic to install all air diffusers in the department.

In a deep aeration tank with a water depth of 10 m, the water depth is 5
The oxygen transfer efficiency of the drainage base is 15% when the air diffuser is installed in the middle part of the m, and the oxygen amount in the air at 20 degrees Celsius under 1 atmosphere is 0.277 kgO ₂ / m ^{3 of} air. If so, the above-mentioned 1.2-2.4 kgO ₂ / m ^{3 of} tank m.
Dividing 277 kgO ₂ / m ³ of air by 0.15 gives 29 ~
58m ³ air m ³ / tank m ³ days, 300 × 300 ×
80 liters of air per 30 mm diffuser plate
When minute to, diffuser plate number becomes 0.25 to 0.50 sheets / tank m ^3. Since the area of the diffuser plate is 0.09 m ² / sheets, diffuser plates footprint becomes 0.023 ~0.045 m ² / tank m ^3. On the other hand, the water area per 1 m ^{3 in} a deep aeration tank with a water depth of 10 m is 0.1 m.
^{Since it is 2} / tank m ³ , the ratio of the diffuser plate installation area to the water area is 0.023 to 0.045 m ² ÷ 0.1 × 100 = 23 to
Since the diffuser plate is installed only on one side (one side) of the partition wall, the ratio of the diffuser plate installation area to the water area on one side (one side) is 46 to 90%. In the middle-stage aeration type deep aeration tank with air diffuser installed on only one side, if the area occupied by the air diffuser becomes too large, the swirling flow collides with the air diffuser and the resistance increases, causing normal circulation. Will not occur and the carrier will settle to the bottom of the deep aeration tank. According to the test results, in order to perform the aeration by the normal swirling flow, the ratio of the diffuser plate installation area to the water area is 25% or less (the opening area is 75% or more, the water area on one side is 5% or less).
0% or more), the amount of oxygen that can be supplied in the middle aeration type deep tank aeration tank is 1.2 kgO ₂ which is the amount of O ₂ supplied when 46% is provided on only one side of the partition wall.
/ Tank m ^{3 The} maximum oxygen level per day is the maximum.

As described above, the deep aeration tank provided with the air diffuser on the middle part of one side (one side) of the partition wall of the deep aeration tank has a limited area where the air diffuser can be installed. Therefore, there is a problem in that the installation area is insufficient only in the middle part, and it is not possible to supply sufficient air necessary for removal of BOD, nitrification of nitrogen, and precipitation of carrier and sludge. So BO
In addition to supplying the air necessary for removing D and nitrifying nitrogen,
In order to supply the air necessary to prevent the sedimentation of the carrier and sludge, it was considered to install a first air diffuser in the middle part of one side and a second air diffuser in the bottom part, and further consider the total air flow. It has been examined from the oxygen transfer efficiency, the power efficiency, etc., how much the ratio of the air amount of the second diffuser to the amount is preferable.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and the problem to be solved is that the middle step portion on one side of the partition wall provided inside the deep tank aeration tank. In the middle-stage aeration type deep tank aeration tank equipped with the air diffuser, the air required for nitrification of nitrogen at the same time as the removal of BOD in the wastewater and the precipitation of sludge and carrier on the bottom of the deep tank aeration tank It is necessary to reliably supply the air required for prevention while maintaining high oxygen transfer efficiency and power efficiency.

[0008]

A first aspect of the present invention for solving the above-mentioned problem is to provide a "first aeration device in a middle part on one side of a deep tank aeration tank having a partition wall in the center thereof". The deep tank aeration apparatus, which is provided with a second air diffuser capable of controlling the air supply amount independently of the first air diffuser at the bottom of the deep tank aeration tank. A second aspect of the invention is to provide a "first air diffuser at the middle part of one side of a deep tank aeration tank having a partition wall in the center, and a first air diffuser at the bottom of the deep tank aeration tank. Is provided with a second air diffuser capable of controlling the amount of air supplied independently of each other, and the amount of supplied air can be controlled independently of each other.

A third aspect of the present invention is that "a deep aeration tank provided with a partition wall in the central portion performs aeration by the first aeration device provided in the middle part of one side of the deep aeration tank, and The operation method of the deep tank aeration device which performs aeration with the second air diffuser provided at the bottom of the.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The first embodiment of the present invention is, as shown in FIG. 1, a middle-stage aeration with a water depth of 8 to 10 m, which simultaneously removes BOD from wastewater such as sewage and organic wastewater by a swirling flow method and nitrifies nitrogen. The second air diffuser is added only to the bottom surface immediately below the first air diffuser in the deep tank aeration tank of the formula. With this device,
It is possible to supply the air necessary for removing BOD, nitrifying nitrogen, and preventing the precipitation of sludge and carrier at the bottom of the deep tank aeration tank. The first air diffuser (3a) provided on one side of the middle part of the partition wall (2) provided inside the middle aeration type deep tank aeration tank (1) is Controller (4
Controlled by a), the amount of air sent by the second air diffuser (5a) provided at the bottom immediately below the first air diffuser (3a) is
It is controlled by a second control device (6a) separately from the first aeration device (3a). Air supply from the first air diffuser (3a),
Due to the air supply from the second air diffuser (5a), B
When the air required for simultaneous removal of OD and nitrification of nitrogen is supplied, a strong swirling flow with a flow velocity of 2 m / min or more at the bottom of the deep tank aeration tank is obtained, so the specific gravity of the carrier is 1.0 ~
There is no sedimentation of the carrier or sludge when using the carrier of 1.1.

The second embodiment of the present invention, as shown in FIG. 2, is provided inside the middle aeration type deep tank aeration tank (1) and is provided on one side of the middle step of the partition wall (2). The first air diffuser (3b) is controlled by the first controller (4b). The second air diffuser is divided into a plurality of units so that precipitation does not occur at the bottom corner of the deep aeration tank. However, one of the divided second air diffusers (5b) is used for feeding. The volume is controlled by the second controller (6b), and the other divided second
The air supply amount of the air diffuser (7b) is controlled by the second controller (8b), but one of the divided second air diffusers (5b
It is preferable to increase the amount of air supplied in b) to increase the amount of air supplied to the corners, which can completely prevent the sludge and the carrier from being precipitated as compared with the first embodiment.

The third embodiment of the present invention is, as shown in FIG. 3, provided on one side of the middle stage of the partition wall (2) provided inside the middle stage aeration type deep tank aeration tank (1). The amount of air supplied by the first air diffuser (3c) is controlled by the first controller (4c), but the second air diffuser (5c provided on the entire bottom surface of the deep aeration tank ) Is the first aeration device (3
It is controlled by a second control device (6c) separately from c).
Since the second air diffuser (5c) aerates the entire bottom surface of the deep aeration tank, the residence time of bubbles becomes longer and the oxygen transfer efficiency can be improved. By the air supply from the first air diffuser (3C) and the air supply from the second air diffuser (5C),
When the air required to remove BOD in the wastewater and nitrify nitrogen is supplied at the same time, the carrier at the bottom of the deep aeration tank is flowing due to the entire surface aeration. .
There is no precipitation of carrier or sludge even when using carrier 1).

The fourth embodiment of the present invention is, as shown in FIG. 4, provided on one side of the middle stage part of the partition wall (2) provided inside the middle stage aeration type deep tank aeration tank (1). The amount of air supplied by the first air diffuser (3d) is controlled by the first controller (4d), but the amount of air sent by the second air diffuser provided on the entire bottom surface of the deep aeration tank is controlled. In terms of air volume, one of the second air diffusers (5d), which is divided into a plurality, is the second controller (6
One diffuser controlled by d) and divided (5d)
Since the amount of air sent to the control unit (6d) is controlled, the amount of air sent to one of the divided corners can be increased, and sludge and carrier can be completely settled as compared with the third embodiment. It becomes possible to prevent it. In addition, the second air diffuser (5d) (7
Since d) is installed on the entire surface, the first aeration device (3
The bubbles formed by d) and the bubbles formed by the second air diffuser (7d) are dispersed in a wide range, and the residence time is long, so that the oxygen dissolution efficiency is improved.

In the middle-stage aeration type deep tank aeration tank, the position of the air diffuser at the middle stage and the position of the air diffuser at the bottom (immediately below, whole surface)
The necessary and sufficient oxygen amount and oxygen transfer efficiency vary depending on the presence or absence of microbial carriers, but in order to remove BOD in wastewater and nitrify nitrogen at the same time, the conventional middle aeration type deep tank aeration tank was modified. In most cases, a second air diffuser is provided at the bottom of the case, so the test results for this case will be introduced. BOD by the conventional middle aeration type deep tank aeration tank
0.3 to 0.5 kg when removing only without carrier
O ₂ / tank m ³ days of oxygen required, oxygen transfer efficiency is 15
Because it is%, required amount of air is 7.22 to 12 air m ³ / tank m ³
Day.

First embodiment middle stage aeration type deep tank exposure
In the air tank, install the second air diffuser only just below the first air diffuser.
The case of providing and performing will be described. BOD removal and nitrogen
When nitrification is performed without a carrier, 0.6-1.2 kgO_Two/
Tank m ^ThreeIt requires daily oxygen supply, but the required oxygen amount is 0.6.
~ 1.2 kgO_Two/ Tank m^ThreeNo. 1 in the middle of the existing day
0.3 to 0.5 kgO from 1 air diffuser_Two/ Tank m^ThreeOxygen of the day
, The oxygen transfer efficiency is 15%.
The required air volume for the air diffuser is 7.22-12 m^Three/ Tank m^ThreeDay
Becomes Required amount of oxygen 0.6-1.2 kgO_Two/ Tank m^ThreeDay
From 0.3 to 0.5 kgO supplied from the first diffuser_Two
/ Tank m^Three0.3-0.7 kgO minus the daily oxygen_Two/ Tank
m ^ThreeOxygen for the day is stored in the second oxygen diffuser directly below the first air diffuser.
Supplied from the air diffuser. Air generated from the diffuser at the bottom
Bubbles have a long residence time and the oxygen transfer effect is higher than that of the middle aeration type.
The rate will improve. Aerating only with an air diffuser just below the bottom
The oxygen transfer efficiency obtained from the preliminary test results,
If 30% is used, the required air volume is 3.09 to 7.22 air m^Three/
Tank m^ThreeIt will be the day. First air diffuser and second air diffuser tanks
100m^ThreeIf you take the ratio of the amount of air per day, 722 ~
1200 m^Three : 361 ~ 842 air m^Three= 1: 0.30 to 1.17
You. Air volume of the first air diffuser of the middle aeration type deep tank aeration tank
And the amount of air in the second diffuser,
The oxygen transfer efficiency of the body is determined.

A third embodiment of the middle-stage aeration type deep tank aeration tank will be described in which a second air diffuser is provided on the entire bottom surface of the deep layer aeration tank. , BOD removal and nitrogen nitrification without a carrier, 0.6-1.2 kgO ₂ /
Oxygen needs to be supplied for ³ days, but the required oxygen amount is 0.6.
To 1.2 KGO Of ₂ / tank m ³ days, the supply of oxygen of 0.3 to 0.5 KGO ₂ / tank m ³ days from the first air diffuser provided in the middle of an existing, since the oxygen transfer efficiency is 15% , First
Required amount of air in the air diffuser becomes 7.22 to 12 air m ³ / tank m ³ days. Required amount of oxygen 0.6-1.2 kgO ₂ / tank m ³ days minus the above 0.3-0.7 kgO ₂ / tanm m ³ days of oxygen is supplied from the second diffuser installed on the entire bottom surface. . The bubbles generated from there are dispersed over a wide range, the rise is delayed by the swirling flow, and the residence time is long, so the oxygen transfer efficiency is improved compared to the middle-stage aeration type. When using an air diffuser on the entire bottom surface for aeration, using 35% of the oxygen transfer efficiency obtained from the preliminary test results, the required air volume is 3.09 ~
7.22 Air m ³ / tank m ³ days. First air diffuser and second
When the ratio of the amount of air with the air diffuser of 100 m ³ per day is taken, 722 to 1200 air m ³ : 309 to 722 air m ³ =
1: 0.26 to 1.00. First middle-stage aeration type deep aeration tank
The oxygen transfer efficiency of the deep tank aeration tank as a whole is determined by combining the air amount of the air diffuser and the air amount of the second air diffuser.

In the case of performing this in the first embodiment in a deep aeration tank of the middle stage aeration type, in which the second air diffuser is provided just below the first air diffuser and 10% of the carrier is added. explain. , BOD removal and nitrification of nitrogen are carried out by adding 10% of the carrier, it is necessary to supply oxygen of 1.2 to 2.4 kgO ₂ / m ^{3 of} tank m ³ , but the required oxygen amount is 1.2 to 2.4 kgO _2.
/ Of tank m ³ days, the supply of oxygen of 0.3 to 0.5 KGO ₂ / tank m ³ days from the first air diffuser provided at the middle of the existing,
Since the oxygen transfer efficiency is 15%, the required air volume of the first air diffuser is 7.22 to 12 air m ³ / tank m ³ days. Required amount of oxygen 1.2 to 2.4 kgO ₂ / tank m ³ days subtracted the above from 0.9 to 1.9 kgO ₂ / tanm m ³ days of oxygen is supplied from the second diffuser directly below the first diffuser. It The bubbles generated from the second air diffuser have a long residence time,
When using an air diffuser just below the bottom to perform aeration, using 30% of the oxygen transfer efficiency obtained from the preliminary test results, the required air volume is 11 to 23 air m ³ / tank m ³ days. . When the ratio of the air amount per day in the tank 100 m ³ of the first air diffuser and the second air diffuser is taken, 722 to 1200 air m ³ : 1100
Up to 2300 air m ³ = 1: 0.92 to 3.19.

In the third embodiment, this is the middle stage aeration type
In the deep aeration tank, the second diffuser is installed on the entire bottom surface of the deep aeration tank.
Explanation about the case of setting up the container and adding 10% of the carrier
I do. , BOD removal and nitrogen nitrification by adding 10% carrier
1.2 to 2.4 kgO_Two/ Tank m^ThreeOxygen of the day
The required oxygen amount is 1.2 to 2.4 kgO.
_Two/ Tank m^ThreeThe first air diffuser installed in the existing middle stage of the day
From 0.3 to 0.5 kgO_Two/ Tank m^ThreeSupply oxygen for the day
Oxygen transfer efficiency is 15%, so the required air volume is 7.
22 ~ 12m^Three/ Tank m^ThreeIt will be the day. Oxygen requirement 1.2-2.4
kgO_Two/ Tank m^ThreeSubtract the above from the day 0.9-1.9
kgO_Two/ Tank m^ThreeThe oxygen of the day is the second on the bottom.
Supplied from a diffuser. The bottom air diffuser is provided on the entire surface
The air bubbles generated from the
Dispersed, swirling flow suppresses rise and long residence time
Therefore, the oxygen transfer efficiency is improved as compared with the middle aeration type. Bottom
Preliminary test results when aerating device is installed over the entire surface for aeration
Using 35% of the oxygen transfer efficiency obtained from
Volume is 9.28-19.6 m^Three/ Tank m^ThreeIt will be the day. First
100m tank of air device and second air diffuser^ThreePer day
722 to 1200 air m^Three: 928-19
60 air m^Three= 1; 0.77 to 2.71. In addition, use in the aeration tank.
Determining how much oxygen in the supplied air was transferred to the liquid
The oxygen transfer efficiency that indicates the
Supervising the sewerage department of the provincial city bureau, sewerage facility planning and design guidelines and solutions
Theory, 1994 Edition, Chapter 5, "Acid by Aeration"
Based on the formula (Formula 5-108) described in "Elementary dissolution mechanism"
Calculated.

[0019]

[Example] A medium aeration type deep tank aeration tank with a water depth of 10 m was prepared by adding a carrier and installing a first air diffuser at a water depth of 4.8 m and a second air diffuser at a water depth of 9.5 m. , The air volume of the second air diffuser to the total air volume is 60% (first
Air volume of the air diffuser of 2; Air volume of the second air diffuser = 1; 1.
50), the total air amount and the oxygen supply amount (kgO ₂ / kgO ₂ / the air amount of the first air diffuser and the air amount of the second air diffuser)
Fig. 5 shows the result of the test with fresh water for the relationship with the tank m ³ days). The total air amount and the oxygen transfer power efficiency (kgO ₂
FIG. 6 shows the result of testing the relationship with / kwh) with fresh water. Here, the mark ● of the first embodiment is the first embodiment.
In the middle aeration type deep tank aeration tank, the second air diffuser is provided only directly below the first air diffuser, and the second embodiment is used.
The circle mark indicates that the second diffuser is provided on the entire bottom surface of the middle-stage aeration type deep tank aeration tank, and the X mark in the comparative example indicates the middle-stage aeration type deep tank aeration tank. Only the first air diffuser is provided in the middle section on one side.

Looking at the relationship between the total air amount (air m ³ / tank m ³ days) and the oxygen supply amount (kgO ₂ / tank m ³ days), as shown in FIG. The examples 1 and 2 are superior to the comparative examples in all ranges. Further, looking at the relationship between the oxygen transfer power efficiency (kgO ₂ / kwh) with respect to the total air amount (air m ³ / tank m ³ day), as shown in FIG. The examples 1 and 2 are superior to the comparative examples in all ranges. In addition, in comparison with Example 1 in which the second air diffuser was provided only just below the ● mark, Example 2 in which the air diffuser was provided on the entire bottom surface of the ○ mark had a higher oxygen supply amount and oxygen content. The reason why the transfer power efficiency is improved is that the oxygen transfer efficiency is improved by aeration of the entire surface from the bottom.

Table 1 shows that the oxygen supply amount is 2.2 to 2.5 kgO ₂ /
The details of the treatment conditions of Example 1 and Example 2 and the comparative example are extracted and compared in the case where the conditions of the tank m ³ days are almost the same. In the comparative example of the conventional middle-stage aeration type deep tank aeration tank, the installation area of the first air diffuser is 40
% (80% of the water area on one side), too much swirling flow was not obtained, and when supplying 51 m ³ of air only from the middle stage, the oxygen supply amount was 2.16 (kgO ₂ / tank m ³ days). ), The oxygen transfer efficiency is 14.8%, and the oxygen transfer power efficiency is 1.
52 (kgO ₂ / kwh). On the other hand, in the case of Example 1 in which the second air diffuser is provided only directly below, the oxygen supply amount is 2.25 when air of 13 m ³ from the middle stage and 19 m ³ from the bottom is supplied for a total of 32 m ^3. (kgO ₂ / tank m ³
The total oxygen transfer efficiency of the first air diffuser and the _second air diffuser is 25.4%, and the oxygen transfer power efficiency is 1.90 (kgO ₂ / kwh). Also, the second
If the air diffuser is installed on the entire bottom surface,
3m ^3, the oxygen supply amount in the case from the bottom of the first embodiment in which air is supplied in total 32m ³ in 19 m ³ is 2.49 (KGO ₂ / tank m ³ days), variance of the first diffusion device and the second The total oxygen transfer efficiency with the gas device has reached 28.1%, and the oxygen transfer power efficiency is 2.07 (kgO ₂ / kwh).

[Table 1] As described above, in comparison with the comparative example, the present invention achieves a high oxygen transfer efficiency and a high oxygen transfer power efficiency by securing a small amount of air, and sludge to the bottom of the deep aeration tank. It also eliminates the precipitation of carriers. The amount of oxygen supplied (kgO ₂ / m3 day) was 0.277 (kgO ₂ / kgO ₂ / kgO ₂ / m ³ day) based on the amount of air supplied to the deep aeration tank.
m ³ air) to calculate the amount of oxygen, and this was obtained by dividing this by the tank volume. Also, the oxygen transfer power efficiency (k
gO ₂ / kwh) indicates the amount of oxygen dissolved in the liquid per unit power, and is indicated by the ratio of the oxygen transfer rate to the consumption power of the air diffuser. , Sewer facility planning / design guidelines and explanations, 1
It was calculated based on the formula (5-110 formula) described in Chapter 5, "Oxygen dissolution mechanism by aeration" of "1994 version".

According to the present invention, the first air diffuser is provided in the middle stage portion on one side of the deep tank aeration tank having the partition wall in the center.
It is a deep tank aeration device that has a second air diffuser at the bottom of the deep tank aeration tank that can control the amount of air supplied independently of the first air diffuser, but it is necessary for removing BOD and nitrifying nitrogen. It is preferable to set the ratio of the amount of air supplied to the second air diffusing device to the total amount of air in order to supply the necessary air to prevent the precipitation of the carrier and sludge. I examined whether. In a deep aeration tank of medium aeration type with a depth of 10 m with a carrier added, the first diffuser is set to one side at a depth of 4.8 m with a diffuser plate area of 10% of the water area, and at a depth of 9.5 m. The second air diffuser is installed at 15% of the water diffuser plate area, and the total air volume is 32 m ³
/ Tank m ³ days tested with fresh water. FIG. 7 shows the relationship between the oxygen supply amount (kgO ₂ / tank m ³ day) when the ratio of the air amount of the first air diffuser and the air amount of the second air diffuser is changed as Example 2 in FIG. 8 shows the relationship with the oxygen transfer power efficiency (kgO ₂ / kwh) as Example 2 and FIG. 9 shows the relationship with the bottom flow velocity (cm / sec) at the bottom of the deep aeration tank as Example 2. .

From FIG. 7, when the total air amount is 100%, the ratio of the air amount of the second air diffuser provided at the bottom is 40%.
In the range of less than%, the required oxygen supply amount of 2 kgO
_{Since 2} / tank m ³ days cannot be satisfied, it is understood that the ratio should be 40% or more. From FIG. 8, when the total air amount is 100%, the air amount of the second air diffuser is 50%.
In the range of up to 90%, the oxygen transfer power efficiency (kgO
₂ / kwh) is high, so it is preferable to set this range. From FIG. 9, when the air amount of the second air diffuser exceeds 90% when the total air amount is 100%, the critical flow velocity for preventing sludge settling at the bottom of the deep aeration tank is obtained. Since the bottom flow velocity of 5 cm / sec cannot be satisfied, it is understood that the ratio should be 90% or less. Summarizing the above results, first, the ratio of the air amount of the second air diffuser when the total air amount is 100% must be in the range of 50 to 90%.
It can be seen that the higher range of (kgO ₂ / kwh) is preferably in the range of 60 to 90%, and more preferably in the range of 70 to 80%. Actually, there are many cases in which the conventional middle stage aeration type deep tank aeration tank is modified and a second air diffuser is provided at the bottom of the case, and the specifications of the first air diffuser are various. It is considered economical to utilize this device to supply the deficient air by the second air diffuser provided at the bottom.

As seen from the test results, the first air diffuser provided in the middle stage on one side of the deep tank aeration tank having the partition wall in the center has a short distance to the water surface, so that the oxygen in the bubbles is The residence time for dissolution in water is short and the oxygen transfer efficiency is 15
% Is low. On the other hand, since the second air diffuser provided at the bottom has a long distance to the water surface, the residence time for the oxygen in the bubbles to be dissolved in water is long, and the first air diffuser and the second air diffuser
The total oxygen transfer efficiency of the air diffuser is 2
It is as high as 5-28%. In particular, in the present invention, the swirling flow generated by the aeration of the first air diffuser provided in the middle stage portion on one side of the deep aeration tank is the same as the upward flow of the second air diffuser provided in the bottom portion. It is considered that, because the rise is suppressed, the residence time for the oxygen in the bubbles to be dissolved in water is lengthened, and the oxygen transfer power efficiency is improved. The bottom flow velocity for preventing sludge settling at the bottom of the deep aeration tank is secured mainly by the first air diffuser installed in the middle stage, and the air required for BOD removal and nitrogen nitrification is mainly used. It is considered preferable to secure it by a second air diffuser provided at the bottom.

[0025]

As is clear from the above description, the present invention has the following effects. BO could not be achieved by the conventional method due to insufficient air volume.
Obtained a deep tank aeration tank capable of supplying air necessary for removal of D, nitrification of nitrogen, and prevention of carrier and sludge precipitation. By utilizing the blower of the existing deep tank aeration system, the air diffuser installed in the middle stage, and the partition wall to add an air diffuser to the bottom of the deep aeration tank, the equipment cost can be reduced and excellent oxygen can be obtained. Obtained transfer power efficiency and oxygen transfer power efficiency.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a deep tank aeration tank showing a first embodiment of the present invention. (The air supply amount of the air diffuser of the second air diffuser provided directly below is collectively controlled)

FIG. 2 is a vertical sectional view of a deep tank aeration tank showing a second embodiment of the present invention. (The air supply amount of the air diffuser of the second air diffuser provided directly below is divided and controlled)

FIG. 3 is a vertical sectional view of a deep tank aeration tank showing a third embodiment of the present invention. (The air supply amount of the air diffuser of the second air diffuser provided on the entire surface is collectively controlled)

FIG. 4 is a vertical sectional view of a deep tank aeration tank showing a fourth embodiment of the present invention. (The air supply amount of the air diffuser of the second air diffuser provided on the entire surface is divided and controlled)

FIG. 5 shows the relationship between the amount of air and the amount of oxygen supply in Examples 1 and 2.

FIG. 6 shows the relationship between the amount of air and the oxygen transfer power efficiency in Examples 1 and 2.

FIG. 7 is a relation between the air amount ratio and the oxygen supply amount of the first and second air diffusers.

FIG. 8 is a diagram showing the relationship between the air amount ratio and the oxygen transfer power efficiency of the first and second air diffusers.

FIG. 9 shows the relationship between the air volume ratio of the first and second air diffusers and the bottom flow velocity at the bottom.

FIG. 10: Conventional swirl flow type standard aeration device

FIG. 11: Conventional full-aeration standard aeration device

[Fig. 12] Conventional middle-stage aeration type deep tank aeration device

[Explanation of symbols]

1 Deep Aeration Tank of Embodiment 2 Partition Wall of Deep Aeration Tank of Embodiment 3a.3b.3c.3d First Aeration Device of Embodiment 4a.4b.4c.4d First Aeration Device of Embodiment First control device 5a.5b.5c.5d Second air diffusing device of the embodiment 6a.6b.6c.6d Second control device 7a.7b.7c.7d of the embodiment Second aeration device 8a.8b.8c.8d in the case of multiple operations Second control device in the case of multiple embodiments 11 Conventional swirl flow type standard aeration tank 13 Conventional swirl flow type standard aeration tank Air diffuser 14 Conventional swirl type standard aeration tank controller 21 Conventional full aeration standard aeration tank 23 Conventional full aeration standard aeration tank air diffuser 24 Conventional full aeration standard aeration Tank control device 31 Conventional middle-stage aeration type deep tank aeration tank 32 Conventional middle-stage aeration type deep tank aeration tank partition wall 33 Conventional middle-stage aeration type deep tank aeration tank diffuser 34 Conventional middle-stage aeration type Control of deep tank aeration tank apparatus

Claims (5)

[Claims] 1. A first air diffuser is provided in a middle part of one side of a deep tank aeration tank having a partition wall in the center, and the bottom of the deep tank aeration tank is independent of the first air diffuser. A deep tank aeration device characterized in that a second air diffuser capable of controlling the air supply amount is provided. 2. The deep tank aeration apparatus according to claim 1, wherein the second air diffuser is provided on the entire bottom surface of the deep tank aeration tank. 3. The deep aeration tank is provided with a plurality of second air diffusers at the bottom thereof, and the amount of air supplied to each of them is independently controllable.
The deep tank aeration apparatus described in. 4. A deep air aeration tank having a partition wall in the central portion for aeration by a first air diffuser provided at the middle part of one side of the deep aeration tank and a second aeration device provided at the bottom of the deep aeration tank. A method for operating a deep tank aeration device, which comprises aeration with an air diffuser. 5. The ratio of the air amount of the second air diffuser provided at the bottom to the total air amount is 50 to 90%.
The method for operating the deep tank aeration system according to 1.