JP7310333B2 - biological treatment equipment - Google Patents

Description

The present invention relates to a biological treatment apparatus for aerobic biological treatment of organic wastewater such as sewage and industrial wastewater using a plurality of aeration tanks, and more particularly to technology for controlling the amount of air supplied to each aeration tank.

In a biological treatment apparatus having an aeration tank, control is performed so that an appropriate amount of air is supplied to the aeration tank. Patent Document 1 describes connecting a plurality of blowers in parallel to one aeration tank and controlling the air volume of the blowers so as to achieve a target DO (dissolved oxygen) concentration.

In Patent Documents 2 and 3, in a biological treatment apparatus having a plurality of aeration tanks, in order to control the DO concentration of each aeration tank, a blower is connected to the diffuser pipe of the aeration tank for each aeration tank, and the target It is described that the air volume of the blower is controlled so that the DO concentration of .

In Patent Documents 4 and 5, one main pipe connected to one or more blowers is branched to each aeration tank with a valve having one or more flow rate adjustment mechanisms, and the blowers are operated so that the pressure is constant. It is stated that When the DO concentration deviates from the target value, the DO concentration is adjusted by adjusting the opening of a valve provided with a flow control mechanism.

JP-A-6-142678 JP-A-5-220495 JP-A-7-185584 Japanese Patent No. 5714355 JP 2012-200705 A

When controlling the DO concentration in each aeration tank in a biological treatment apparatus having a plurality of aeration tanks, the methods of Patent Documents 2 and 3 use a blower (and a preliminary blower) and a pipe connecting the blower and the aeration tank for each aeration tank. In addition to the high equipment cost, the large-scale configuration results in a large installation space.

On the other hand, in the methods of Patent Documents 4 and 5, it is sufficient to install a blower (and a spare blower) with the minimum required air volume capable of blowing the total air volume of each aeration tank, and the blower cost can be reduced. In addition, the connection between the blower and each aeration tank can be achieved by bypassing the branch pipe from the common pipe connected to the blower to each aeration tank, thereby reducing the piping installation cost. It is also possible to reduce the total installation space.

However, in the methods of Patent Literatures 4 and 5, if the opening of the valve provided with the flow control mechanism is kept small for a long period of time, the motor and head of the blower become hot, causing abnormalities such as excessive temperature rise. In addition to this, there was a concern that the load on the motor unit would increase, causing overcurrent in the motor unit and causing failure. In addition, when the opening of the valve equipped with the flow rate adjustment mechanism is small, even if the average dissolved oxygen concentration in the entire aeration tank is sufficient, the fluidity in the aeration tank is partially reduced. As a result, the dissolved oxygen concentration in the aeration tank locally decreases, sludge accumulates on the bottom of the reaction tank, and problems such as odor caused by putrefaction of microorganisms may occur.

An object of the present invention is to provide a space-saving biological treatment apparatus capable of performing stable aeration control.

The biological treatment apparatus of the present invention is a biological treatment apparatus comprising an aeration tank and an air blower for supplying air for aeration to an air diffusion member of the aeration tank, wherein the air blower comprises a blower and a blower. A main pipe connected to the aeration tank, a plurality of branch pipes branching from the pipe, and a valve provided in each branch pipe, and the first branch pipe has a predetermined oxygen concentration regardless of the dissolved oxygen concentration in the aeration tank. A valve for adjusting the degree of opening is installed, and another second branch pipe is provided with a valve for controlling the flow rate according to the dissolved oxygen concentration in the aeration tank.

In one aspect of the present invention, a plurality of the second branch pipes are provided, and each second branch pipe is provided with an on/off valve.

In one aspect of the present invention, the second branch pipe is provided with a proportional control valve.

In one aspect of the present invention, a plurality of aeration tanks are installed in series or in parallel.

In one aspect of the present invention, a manual valve is installed in the first branch pipe.

In one aspect of the present invention, the degree of opening of the manual valve is such that the blower does not motor trip even when all the valves of the second branch pipe are closed, and the fluidity in the aeration tank is ensured. is set to

According to the biological treatment apparatus of the present invention, even when the set value of the dissolved oxygen concentration in the aeration tank is small, air can be stably blown without causing an excessive temperature rise in the blower.

In addition, according to the biological treatment apparatus of the present invention, even when the set value of the dissolved oxygen concentration in the aeration tank is small, by blowing air so as to ensure the minimum necessary fluidity in the aeration tank, the sludge in the aeration tank deposition and microbial putrefaction can be prevented.

1 is a configuration diagram of a biological treatment apparatus according to an embodiment; FIG. 1 is a configuration diagram of a biological treatment apparatus according to an embodiment; FIG. 1 is a configuration diagram of a biological treatment apparatus according to an embodiment; FIG. 1 is a configuration diagram of a biological treatment apparatus according to an embodiment; FIG. It is a block diagram of the biological treatment apparatus which concerns on a comparative example.

Embodiments will be described below with reference to FIGS.

FIG. 1 shows the first embodiment, in which raw water (organic wastewater) is sequentially treated in a first aeration tank 1 and a second aeration tank 2 connected in series to produce treated water. Although the aeration tanks 1 and 2 are installed in series in FIG. 1, they may be installed in parallel. The number of aeration tanks may be 3 or more in either case of series or parallel.

Aeration tanks 1 and 2 are provided with diffuser pipes 3 and 4, respectively. The diffuser pipe may be of a diffuser type, a coarse bubble type, a tubular membrane type, or the like, and is not particularly limited.

DO meters 5 and 6 are installed in each of the aeration tanks 1 and 2, respectively. Detection signals from the DO meters 5 and 6 are input to the control device 7 . A blower 8 is controlled by a control device 7 . Air from the blower 8 is blown through the main pipe 9 . The main pipe 9 is provided with a pressure gauge 9a.

In this embodiment, relay pipes 10 and 20 are connected to the main pipe 9 . Each relay pipe 10, 20 branches into four branch pipes 11, 12, 13, 14 and 21, 22, 23, 24.

The branch pipes 11 and 21 are first branch pipes, and are provided with manual valves 31 and 41 whose opening can be manually adjusted.

The branch pipes 12 to 14 and 22 to 24 are second branch pipes, and are provided with on/off valves 32 to 34 and 42 to 44, which are electromagnetic valves that are switched between open and closed by the control device 7, respectively.

The branch pipes 11 to 14 are connected to a joint pipe 15 downstream of the valves 31 to 34 , and the joint pipe 15 is connected to the diffuser pipe 3 . The branch pipes 21 to 24 are connected to a confluence pipe 25 downstream of the valves 41 to 44 , and the confluence pipe 25 is connected to the diffuser pipe 4 .

In this embodiment, the manual valves 31 and 41 are always opened at a predetermined degree of opening, and the on/off valves 32 to 34 and 42 to 44 are switched between on and off (opening and closing) to allow the diffusion pipes 3 and 4 to open. Aeration air volume from is controlled.

The operation of the blower 8 is controlled so that the internal pressure of the main pipe 9 detected by the pressure gauge 9a is kept constant within a set range. Although only one blower 9 is shown in FIG. 1, a plurality of blowers are installed side by side. may be controlled to reduce the number of operating units.

Although four branch pipes 11 to 14 and 21 to 24 are provided for each aeration tank in FIG. 1, the number may be two, three, or five or more. Practically, about 2 to 5 is suitable.

In FIG. 2, three branch pipes 11-13 and 21-23 are provided. 1, manual valves 31, 41 are installed in the first branch pipes 11, 21, respectively, and on-off valves 32, 33, 42, 43 are installed in the second branch pipes 12, 13, 22, 23. there is Other configurations in FIG. 2 are the same as in FIG. 1, and the same reference numerals denote the same parts.

1 and 2, relay pipes 10 and 20 are branched from the main pipe 9, and branch pipes 11 to 14 (or 11 to 13) and 21 to 24 (or 21 to 23) are branched from the relay pipes 10 and 20. However, as shown in FIG. 3, the branch pipes 11 to 13 and 21 to 23 are branched directly from the main pipe 9, and the terminal side of each branch pipe 11 to 13 and 21 to 23 is directly connected to the air diffuser 3 or 4. may be connected. In FIG. 3, only the downstream sides of the branch pipes 11 to 13 and 21 to 23 may be connected to the combined pipes 15 and 25, respectively, and the combined pipes 15 and 25 may be connected to the diffuser pipes 3 and 4.

As shown in Figures 1 to 3, when on-off valves are used as the flow rate variable mechanism, each on-off valve is set so that the set air volume set based on the target value of DO concentration is ventilated when all the on-off valves are open. It is preferable to adjust the degree of opening. In this case, it is desirable to keep the same amount of air blown for each on/off valve when all the on/off valves are open. By doing so, it is possible to equalize the amount of increase in air volume when the number of open on/off valves is increased in stages.

Regarding the manual valves 31, 41, the opening degree is adjusted in advance so that the blower does not trip even when all the on-off valves are closed, and the minimum flow rate that can secure the fluidity in the aeration tanks 1 and 2 is obtained. It is desirable to

During operation of the biological treatment apparatus, when the measured value of DO concentration is greater or less than the target range of DO concentration, one of the on/off valves is closed or opened to change the amount of air supplied. The above adjustment is repeated based on the measured value of the DO concentration after the lapse of a predetermined time, and the air volume is changed stepwise.

After one adjustment, it is preferable to provide an interval of at least one minute or more before the next adjustment.

Table 1 shows the on/off valve opening/closing pattern and the ventilation air volume at that time in the case of FIG. 1 where the number of on/off valves installed is three.

When the measured value of the DO concentration is smaller than the target range of the DO concentration, the degree of opening of the on/off valve is changed stepwise from pattern 1 to pattern 4 to increase the ventilation air volume.

When the measured value of the DO concentration is larger than the target range of the DO concentration, the degree of opening of the on/off valve is decreased stepwise from pattern 4 to pattern 1 to reduce the ventilation air volume.

In Pattern 1, if the measured value of DO concentration is higher than the target range of DO concentration, the oxygen supply is sufficient, but the manual valve is not closed to prevent motor trip and ensure fluidity in the reaction vessel. , the setting is not changed from pattern 1.

Also, if the measured value of DO concentration is smaller than the target range of DO concentration in pattern 4, it is considered to be in an overloaded state. Investigate and consider the problem of the surface, and do not change the setting from pattern 4.

1 to 3, on/off valves are used, but as shown in FIG. 4, proportional control valves 35 and 45 may be used to continuously change the degree of opening to adjust the amount of blown air. In FIG. 4, manual valves 31 and 41 are provided on first branch pipes 11 and 21, and proportional control valves 35 and 45 are provided on second branch pipes 12 and 22, respectively. 4, the branch pipes 11, 12, 21 and 22 may be directly connected to the main pipe 9 and the diffuser pipes 3 and 4, respectively.

In the biological treatment apparatus of FIG. 4, when the measured value of the DO concentration in the aeration tank is larger or smaller than the target range of the DO concentration, the DO is the control variable, and the opening of the proportional control valves 35 and 45 or the air volume is the manipulated variable. The air volume is changed by implementing PID control. The above adjustment is repeated based on the measured value of the DO concentration after the lapse of a predetermined time.

In the biological treatment apparatus of FIG. 4, each of the aeration tanks 1 and 2 may be provided with a plurality of second branch pipes, and each second branch pipe may be provided with a proportional control valve. In this case, when changing the opening of each proportional control valve, it is desirable to perform interlocking control so that the opening of all the proportional control valves connected to one aeration tank is the same.

[Example 1]
In the biological treatment apparatus of FIG. 2, air was blown and aerated in the aeration tanks 1 and 2, which consist of polyurethane sponge carrier-filled tanks (carrier filling rate: 25%) having the following configuration.

Volume of first aeration tank 1: 1,000 m ³
Volume of second aeration tank 2: 600 m ³
Raw water TOC: 100mg/L (synthetic wastewater)
Average raw water flow rate: 150 m ³ /h
Maximum raw water flow rate: 180 m ³ /h
Minimum raw water flow rate: 0 m ³ /h

Table 2 shows the required DO concentration for each raw water flow rate.

In addition, the following valves 31-34 and 41-44 are provided.

Aeration tank 1: 80A manual valve and two 100A on/off valves Aeration tank 2: 80A manual valve and two 80A on/off valves Aeration tank: 1,000 m ³ /h, second aeration tank: 600 m ³ /h).

Assuming that the raw water flow rate fluctuates about 50 m ³ /h in 2 hours and fluctuates between 0 and 180 m ³ /h in 24 hours, continuous operation is performed for 2 hours at each of 5 types of flow rates, and the DO concentration is set. When the concentration exceeded or fell below the range (set value ±0.5 mg/L), one ON/OFF valve was switched from closed to open or from open to closed to automatically control the DO concentration. The time intervals between the opening and closing of the valve were measured to calculate the average value, and the occurrence of blower thermal trip was observed. Table 3 shows the results.

As shown in Table 3, the DO concentration could be controlled within a predetermined range by switching the opening and closing of the on/off valve at intervals of 2 to 10 minutes on average. Also, no thermal trip occurred.

[Example 2]
In Example 1, the operation was performed under the same conditions as in Example 1, except that the configuration of the branch pipes was as shown in FIG. The results were exactly the same as in Example 1 (as shown in Table 3 above).

[Comparative Example 1]
As shown in FIG. 5, the relay pipes 10 and 20 are provided with proportional control valves 35 and 45, respectively, and are directly connected to the diffuser pipes 3 and 4, and the branch pipes 11 to 14 and 21 to 24 are omitted. , 2 was operated.

The proportional control valve 35 is a 150A control valve, and the proportional control valve 45 is a 100A control valve.

As in Examples 1 and 2, assuming that the raw water flow rate fluctuates by about 50 m ³ /h in 2 hours and fluctuates between 0 and 180 m ³ /h in 24 hours, five types of flow rates are continued for 2 hours each. When the DO concentration exceeds or falls below the set range (set value ± 0.5 mg / L), the opening control is performed to decrease or increase the opening of the control valve by 10% with respect to the full opening. The DO concentration was PID-controlled. The opening of the control valve and the occurrence of blower thermal trip were observed. Table 4 shows the results.

As shown in Table 4, the DO concentration was controlled within a predetermined range by appropriately adjusting the opening of the control valve, but a thermal trip occurred during control under low flow rate conditions.

1, 2 Aeration tank 7 Control device 8 Blower 9 Main pipe 10, 20 Relay pipe 11-14, 21-24 Branch pipe 31, 41 Manual valve 32-34, 42-44 On-off valve 35, 45 Proportional control valve

Claims (6)

A biological treatment apparatus comprising an aeration tank and a blower for supplying air for aeration to an air diffusion member of the aeration tank,
The blower is
blower and
a main pipe connected to the blower;
a plurality of branch pipes branching from the main pipe;
a confluence pipe extending from each branch pipe and connected to the diffuser member;
and
The branch pipe consists of a first branch pipe and a second branch pipe,
The first branch pipe is provided with a first valve that opens to a predetermined degree regardless of the dissolved oxygen concentration in the aeration tank,
The second branch pipe is provided with a second valve for controlling the flow rate of the air supplied from the confluence pipe to the diffuser member according to the dissolved oxygen concentration in the aeration tank. A biological treatment device characterized by: 2. A biological treatment apparatus according to claim 1, wherein a plurality of said second branch pipes are provided, and each of said second branch pipes is provided with an on/off valve as said second valve. 2. A biological treatment apparatus according to claim 1, wherein said second branch pipe is provided with a proportional control valve as said second valve . 4. The biological treatment apparatus according to any one of claims 1 to 3, wherein a plurality of said aeration tanks are installed in series or in parallel. 5. The biological treatment apparatus according to any one of claims 1 to 4, wherein a manual valve is installed as said first valve in said first branch pipe. The degree of opening of the manual valve is such that the motor does not trip the blower even when the second valves of all the second branch pipes are closed, and the fluidity in the aeration tank is ensured. 6. A biological treatment apparatus according to claim 5, characterized in that it is set as follows.

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