JPH01293192A - Method of operating aeration device - Google Patents

Abstract

PURPOSE:To stably execute high denitrification and dephosphorization by opening and closing a valve of an air feed port to attain anaeration and aeration states and executing only the stirring by lowering the rotating speed of an aeration machine in an anaeration time zone. CONSTITUTION:A negative pressure is generated in the front end part of a screw 5 and the air is sucked from an air intake port 10 at the front end of an air suction pipe 8 and is released from the front end of the screw 5 into water when a motor 2 is operated to rotate the screw 5 by opening the valve 9 of the aeration device to be used for a biological treatment of org. waste water. The slow stirring to the extent of preventing the sludge in the treatment tank from setting is executed by lowering the rotating speed by an inverter 11 connected to the motor 2 and a control panel 12 and further by closing the valve 9 at the time of only the stirring. The respective states of anaeration and aeration are thus created and the high denitrification and dephosphorization are executed stably without overloading of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of operating an aeration device used in a device for biologically treating organic wastewater.

[Conventional technology]

As a device for biologically treating organic wastewater, Japanese Patent Application Laid-open No. 621
There is a batch processing device known from Japanese Patent No. 80797.

This device uses a self-contained device to create an anaerobic state and an aerobic state over time, and the publication also describes how to reduce the rotational speed to prevent self-inhalation. An operating method is described in which stirring is carried out in the air, and an operating method in which a valve is provided at the air supply port to prevent air supply and only stirring is carried out.

[Problem to be solved by the invention]

However, when achieving an anaerobic state by lowering the rotation speed, as described in the above publication,
It is necessary to lower the rotational speed to 1/2.5 to 1/3 of that of aeration, and the stirring power decreases. As a result, if the water depth of the treatment tank is deep or the tank capacity is large, the sludge will settle and the contact between the sludge and the sewage will be poor. There is a risk that insufficient and stable processing performance may not be obtained.

However, in the latter case, as a result of stopping the air supply, the motor load increases compared to when air is being supplied, that is, when air is being supplied, and the motor has a larger capacity compared to operating in an anaerobic state. I needed to.

[Means to solve the problem]

The present invention uses a valve provided at the air supply port to create anaerobic and aerobic conditions by opening and closing the valve, and
During the anaerobic period, the rotation speed of the aerator is lowered to prevent the motor load from exceeding the rated load set based on the aeration state.

By adopting this operating method, the self-priming aeration unit can maintain a simple stirring state more effectively, and it also prevents the motor from becoming overloaded or by installing a large-capacity motor. It is possible to avoid waste.

〔Example〕

The present invention will be explained below based on examples.

Example 1 FIG. 1 is a schematic diagram of an aeration device 1 used in the present invention installed in an organic wastewater treatment tank. The aeration device 1 has a hollow shaft 3 connected directly to a motor 2, and these are housed in a cover 4. The hollow shaft 3 is provided with an intake lower that communicates with the hollow hole 6 for taking in air, and communicates with the tip of the screw 5 attached to the tip of the hollow shaft 3. The cover 4 is provided with an intake pipe 8 and a valve 9. When the motor 2 is operated with the valve 9 open and the screw S is rotated, negative pressure is generated at the tip of the screw 5, so air is sucked from the air intake port 10 at the tip of the intake pipe 8, and the hollow shaft 3 The air is discharged from the lower intake air through the hollow hole 6 into the water from the tip of the screw 5.

When only stirring is performed, the rotation speed is lowered by the inverter 11 and control panel 12 connected to the motor 2, and the valve 9 is closed, so that the sludge in the treatment tank can be stirred and mixed gently to the extent that it does not settle. Eggplant.

Table 1 shows the circulation waterway type +000
This figure shows the power consumption of the aeration device and the flow velocity in three cross sections when anaerobic stirring operation is performed in the m' water tank under the following three conditions.

Condition 1: The number of revolutions is 11,000 using the method of the present invention.
rp and the valve is closed Condition 2: Only inverter control is performed with the valve open and operation is performed at 500 rpm Condition 3: When the inverter control is not performed and only the valve is closed (rotation The number is 172 Orpm) Table 1 The following points are clear from Table 1.

(+, ) Power consumption is 60Hz, rotation speed 1720rp
The actual measured value when the pulp was opened at a rating of m and was operated carefully was 5
．． On the other hand, conditions 1 and 2 resulted in considerable energy-saving operation, with a value of 1.06 and 0.41, respectively. On the other hand, condition 3 is 8.65
This was approximately 45% higher than when the valve was open, resulting in an overload.

(2) The average flow velocity in the aquarium was 12.4 cm/sec under condition 1, while it was 4.9 cm/sec under condition 2.
In general, it was not possible to satisfy the 10 sounds/second required to prevent sludge from settling. In addition, under condition 3, the flow rate was not measured because it was overloaded and could not be operated for a long time.

Next, the processing effects of the present invention will be described.

The aeration device was fixed to a float and placed in a 40 m3 rectangular water tank (2 m' x 5 m' x 4 m'').
The operation shown in FIG. 2 was carried out with a cycle of 12 hours.

The drawing rate of supernatant water per 1 cycle is set to 1/2, and after the end of the previous cycle, the next operation is started with 20 m3 of mixed liquid remaining, and raw water is first introduced. The raw water will be water from the settling basin of the terminal sewage treatment plant, and the inflow will be completed in three hours. During this period, the anaerobic period was set, and after stirring was carried out for 3 hours according to each method shown in Condition 1 and Condition 2, valve 9 was opened and the normal rotation speed (172
Aeration was carried out for 0.5 hour at 1000 ml (orpm). Dephosphorization and a certain degree of denitrification can be achieved even by performing aeration only once after the anaerobic period, but here, l1
The nitrogen content that was nitrified at 1 atmosphere was denitrified, and anaerobic-aeration was repeated three times to obtain even higher denitrification performance. After the treatment process was completed, the aeration device 1 was stopped, the sludge was allowed to settle, and the supernatant water was drawn out as treated water. Table 2 shows the processing performance for each condition when such operation was performed.

Table 2 In Table 2, Condition 4 is a case where no stirring is performed during the anaerobic time period and the sludge is left to settle.
Compared to condition 1.2 where anaerobic stirring was performed, the BOD removal rate is not much different and shows a high value of over 90%, but under T-
The removal rate of N (nitrogen) and T-P (phosphorus) is under conditions 1 and 2.
It is lower than 70%.

In addition, when comparing conditions 1 and 2, condition 1 has a higher removal rate overall, especially for T-N and T-P, condition 1 shows a removal rate of 90% or more, whereas condition 2 are both 80%
It is as follows. Although both Conditions 1 and 2 are agitated during the anaerobic period, the denitrification and dephosphorization performance of Condition 2 is inferior because the agitation during the anaerobic period is insufficient. This is thought to be because most of the sludge had settled, so contact between the sludge and sewage was not sufficient, and the denitrification reaction and phosphorus release reaction, which were promoted under anaerobic conditions, were insufficient.

The method of performing anaerobic stirring only by controlling the rotation speed using an inverter, as in condition 2, allows for a certain degree of mixing and mixing even at low rotation speeds when used in water depths of about 2 m or less, so it must be operated on an appropriate time schedule. If this is done, denitrification and dephosphorization performance of about 80% can be maintained. However, in the case of a deep water tank, for example, with a depth of 4 m, the stirring flow will not reach the bottom of the tank at low rotation speeds and most of the sludge will settle, so as shown in condition 1 of the present invention, In addition, it is necessary to perform stirring by a method that combines rotational speed control and valve opening/closing.

Regarding the agitation state during the anaerobic time period, the higher the agitation force, the better.In order to prevent the motor from being overloaded, the motor load rate during this anaerobic time period should be 100% or less, and the necessary minimum amount of agitation should be used to prevent the sludge from settling. Just do it. Therefore, when performing anaerobic agitation, it is desirable to understand the relationship between the motor load factor, rotation speed, agitation flow rate, and sludge mixing state, set the rotation speed to the minimum, and perform only valve agitation. Generally, the flow rate to prevent sludge from settling is IO+c+
++/second or more, so as shown in Condition 1 above, 1. A desired stirring state can be obtained by setting the rotational speed to about OOOrpm.

However, since the rotation speed during anaerobic agitation depends on the capacity of the aeration device, the color, capacity, water depth, etc. of the treatment tank, it is desirable to know it before treatment or to adjust it in the actual machine.

As a means of controlling the rotation speed, the rotation speed can be changed freely.
Although the method using an inverter is optimal in terms of energy saving, the method is not necessarily limited to this, and other means such as a ball change motor may also be used. Further, although it is desirable to carry out stirring operation throughout the anaerobic time period, from the viewpoint of energy saving, stirring may be carried out intermittently using a timer.

Example 2 FIG. 3 shows another example of the present invention, which is applied to the oxidation ditch method.

The ditch 21 is an endless circulation waterway partitioned by a central partition wall 22 as shown in FIG.
3 is provided in two places. Although not shown in the figure, this aeration device 23 is provided with a rotation speed control means and an intake pipe valve, and can perform only stirring during the anaerobic period.

Although the number and location of the aeration devices 23 to be installed are not particularly limited, a plurality of aeration devices 23 are usually installed at the position shown in FIG. 3 or in the center of the straight waterway section.

When performing denitrification using the oxidation ditch method, if the ditch capacity is large, nitrification under aerobic conditions and denitrification under anaerobic conditions can be promoted by providing an anaerobic zone and an aerobic zone within the ditch. If the ditch capacity is small and it is difficult to maintain both zones stably, denitrification is performed by repeating anaerobic and aerobic cycles over time. That is, the two aerators installed in FIG. 3 are operated at the same time, and aeration and stirring are alternately repeated in conjunction with the evening, timer, or Do meter. 20
Table 3 shows the treatment performance when two aerators with a temperature of 1.5°C were installed in a ditch with 0 pups as shown in Figure 3 and operated for 1 cycle under the following three conditions during the anaerobic period. .

Condition 5: The number of revolutions is 120Or by the method of the present invention.
pm and stirring with the valve closed Condition 6: With the valve open, C inverter control only, stirring at 500 rpm Condition 7: No stirring, during the anaerobic period Aeration H
When both Sumires were stopped, the anaerobic-aerobic interval for all three conditions was set to 2 hours by timer settings, and operation during the aerobic period was continuous at the rated rotational speed with the valve open.

Table 3 From Table 3, when Condition 5 using the method of the present invention is compared with the other two conditions, Condition 5 shows the highest removal rate for both BOD, TN, and TP.

In particular, the difference in T-N removal rate was large, compared to condition 7 where stirring was not performed during the anaerobic period.
Since the removal rate was about 20% higher than that under condition 6, where stirring was performed at a low speed of 100 pm, it was found that condition 1! ! -15, the agitation rP during the anaerobic period was sufficiently performed, and the sludge and sewage came into sufficient contact with each other, indicating that denitrification progressed.
This is an application of the operating method shown in Publication No. 180797 to the oxidation ditch method, and by performing a certain amount of stirring during the anaerobic period, the denitrification performance is improved somewhat compared to Condition 7 where no stirring is performed. Although
Compared to Condition 5 of the present invention, the denitrification performance was poor, and it is thought that the stirring power was insufficient.

Although the oxidation ditch method is not a process that can be expected to have a great effect on dephosphorization, in Table 3, the T-P removal rate is highest in the order of condition 5, condition 6, and condition 7. It is also desirable to stir as much as possible during the anaerobic period.

〔Effect of the invention〕

According to the present invention, in a biological treatment device using a self-priming aeration device that treats organic wastewater by changing it from an anaerobic state to an aerobic state over time, by simply switching the operation of the self-priming aeration device, anaerobic Since necessary and sufficient stirring is performed during the time period, and necessary oxygen can be supplied by aeration during the aerobic time period, stable and high denitrification and dephosphorization performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a front view of the present invention, FIG. 2 is a driving schedule of the present invention, and FIG. 3 is another embodiment. 1 is an aeration device, 2 is a motor, and 5 is a stirring screw. Figure 3

Claims (1)

[Claims] (1) A method of operating an aeration device of a biological treatment device that treats organic wastewater by changing the state from an anaerobic state to an aerobic state over time, which combines stirring during the anaerobic period and aeration during the aerobic period. During the anaerobic period, a rotation speed control means installed in the aeration device and a valve installed in the intake pipe reduce the rotation speed and close the valve to perform only agitation. , a method of operating an aeration device characterized by performing aeration by increasing the rotation speed and opening a valve during an aerobic period.