JPS60248291A - Apparatus for treating activated sludge - Google Patents

Abstract

PURPOSE:To control easily the amt. of dissolved oxygen in an aeration vessel regardless of variations in influent water by providing a dissolved oxygen meter in the aeration vessel, and turning on and off the operation of an air supply means in correspondence with the signal of said meter. CONSTITUTION:The detection terminal 5 of a dissolved oxygen meter 4 for detecting the concn. of dissolved oxygen in the sewage is provided in an aeration vessel 1, and the dissolved oxygen meter 4 is connected to a controller 6 and further to the electric power source circuit of a blower 3. And when the concn. of dissolved oxygen exceeds the upper limit value, an operation-off signal is outputted to an air supply means, and an operation on signal is outputted when the concn. exceeds the lower limit value. The amt. of dissolved oxygen is controlled surely and easily in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an activated sludge treatment apparatus that allows the amount of dissolved oxygen in an aeration tank to be controlled within a certain range.

Conventional technology One of the conventional activated sludge treatment methods is to collect wastewater in an aeration tank.
There is a long-time aeration method that supplies air from the bottom of the aeration tank. Conventionally, in this system, an aeration blower is activated regardless of the presence or absence of inflow water. Therefore, when there is no inflow water, dissolved oxygen in the aeration tank tends to be excessive. Excessive amounts of dissolved oxygen usually impede the movement of bacteria and lower the pH.

Since there is an environmental restriction on P]-1, an excess amount of dissolved oxygen must be prevented. In addition, if the amount of dissolved oxygen becomes too low, bacteria will die, so this must also be prevented.

One way to control this is to set the aeration blower to intermittent (on/off) operation by setting a timer. However, since the settings for the operating time (on) and stop time (7j) are fixed, there is a problem in that it cannot respond to fluctuations in the amount of inflow water. In addition, in order to cope with fluctuations in the amount of inflow water, some systems used an inverter to continuously vary the rotation speed of the blower drive motor according to the dissolved oxygen concentration, but it was possible to adjust the rotation speed of the motor by 1] is rotating, and there was a problem that excessive aeration would occur if the inflow water stopped.

Purpose of the Invention The purpose of the present invention is to maintain aeration of 1fff regardless of fluctuations in inflow water.
The aim is to easily manage the amount of dissolved oxygen in the inflow water, and in particular, by controlling the amount of aeration according to the dissolved oxygen concentration with basically on/off control, it is possible to easily control the amount of inflow water. It is an object of the present invention to provide an automatic control device for a blower that can handle the following cases.

Structure of the Invention The active 11F sludge 9J1 physical filter of the present invention that meets this purpose
It is equipped with an aeration tank for storing sewage and an air supply means for supplying air to the aeration tank! [Between the sludge treatment stations, a dissolved oxygen sensor is installed to measure the dissolved oxygen concentration in the wastewater in the aeration tank. At the same time, a signal from the dissolved oxygen sensor is input, and that signal is used to measure the dissolved oxygen concentration in the sewage. A control device is installed that outputs a signal to turn off the operation to the air supply means when the upper limit of the concentration marked J is exceeded, and outputs a signal to turn on the air supply means when the lower limit of the dissolved oxygen concentration reaches a preset value. −)
consists of things.

Effect of the Invention In such an activated sludge treatment apparatus, when the air supply means is turned on, the amount of water flowing into the aeration tank decreases or the inflow is stopped, and the amount of dissolved oxygen in the aeration tank decreases. The dissolved oxygen concentration rises and eventually exceeds the set upper limit. Then, a signal is output from the control device in response to the signal from the dissolved oxygen meter, and the operation of the air supply means is turned off and aeration is stopped. If left in this condition,
Dissolved oxygen concentration gradually decreases due to inflow water and natural reduction,
Then the C setting lower limit value is reached. When it is covered, a signal is output from the control device based on the signal from the dissolved oxygen meter, and the operation of the air supply means is turned on and aeration is started. and,
Furthermore, when the amount of inflow water decreases or stops, the dissolved oxygen concentration increases and the same control as described above is repeated.

In this way, the operation of the air supply means is turned on and off based on the dissolved oxygen concentration, and the dissolved oxygen concentration is always between the set upper limit value and the set lower limit value. Compared to the case of operation by setting, the amount of dissolved oxygen r1 is reliably kept within the predetermined regulation range, and
Since it is controlled regardless of whether the inflow water has stopped, an excessive amount of dissolved oxygen can be easily prevented.

4- Effect of the invention Therefore, the air supply means can be operated only when necessary according to the actual dissolved oxygen concentration, preventing excessive aeration and underaeration, and ensuring the amount of dissolved oxygen. And it can be easily managed within a predetermined range.

In addition, since the dissolved oxygen concentration usually changes slowly,
According to the present invention, which aerates only when necessary according to the concentration, it is possible to reduce the number of operations and operation time of the air supply means compared to conventional timer settings. : A large energy saving effect of 1q can be achieved with a low-cost investment such as adding a control device.

EXAMPLES Below, preferred examples of the activated sludge treatment charge of the present invention will be described with reference to the drawings.

FIG. 1 shows an activated sludge treatment apparatus according to an embodiment of the present invention. In the figure, 1 indicates an aeration tank that accommodates wastewater. A pipe 2 having a number of holes is provided at the bottom of the aeration tank 1, and the pipe 2 is connected to a blower 3 as an air supply means.

In the aeration tank 1, a detection end 5 with a cumulative total of 4 dissolved m is provided for detecting the dissolved oxygen concentration in the wastewater. The dissolved oxygen meter 4 is connected to a control device 6, and inputs a signal of detected dissolved oxygen m degrees to the control device 6. The control device 6 controls the blower 3
It is connected to the power supply circuit of the blower 3 and outputs an operation on/off signal to the blower 3.

The control device 6 includes an increaser 7 that appropriately processes the signal from the dissolved oxygen sensor 4, and an increaser 1 that processes the signal from the increaser 1] 7 and upper and lower limit values of the dissolved oxygen concentration set in advance. It is composed of a comparison section 8 for comparing, a control section 9 for emitting a signal based on the comparison result, and a backup circuit 10 for outputting an operation ON/OFF signal for the blower 3 based on the signal from the control section 9. . The backup circuit 10 has a conventional timer setting J:
It is connected to the existing control circuit 11 as an operation control device that controls the reblower 3 on and off. A switching means is provided to select whether or not to send the timer setting signal from the circuit 11.

FIG. 2 shows an example of the details of the enlargement part 7 and the comparison part 8,
FIG. 3 shows an example of details of the backup circuit 10. These will be explained below along with the overall operation of the control device N6.

First, in FIG. 1, dissolved oxygen in the aeration tank 1 is sensed by the detection end 5 and input to the dissolved oxygen meter 4. Dissolved oxygen 1
4 outputs a voltage corresponding to the measured dissolved oxygen concentration. The output voltage from the dissolved oxygen unit 4 is amplified to a voltage that is easy to set and control. Then, a voltage value corresponding to one degree of dissolved oxygen tt is set in advance in the comparator 8, and compared with the input voltage. At this time, the first comparison section sets the upper limit value of the dissolved oxygen concentration, and stops the blower when the input upper limit value is exceeded. A lower limit value is set in the second comparison section, and when the input voltage reaches the set lower limit value, the blower is activated. When the voltage becomes equal to the upper limit set value or the lower limit set value, the relay operates and issues a command to the next backup circuit 10 to start or stop the blower 3. If the selector switch as a means of switching with the existing control circuit 11 is set to the automatic control side, the programmer 93 will be controlled by start and stop commands. The backup circuit 10 includes a restart prevention circuit in order to prevent a hunting phenomenon in which the blower 3 is repeatedly started and stopped. Furthermore, if the detection end 5 or the dissolved oxygen meter 4 breaks down, it is automatically switched to the existing control circuit 11, and a timer allows alternate operation for, for example, two hours. Furthermore, when the selector switch is set to the existing control side, the detection end 5 and dissolved oxygen meter 4 can be removed for inspection and configuration, and during that time, the timer allows alternate operation for 2 hours. Therefore, the existing control circuit 11 operates under the conditions of the backup circuit 10 to operate and stop the blower 3.

Next, control of dissolved oxygen concentration will be explained.

(1) First, operate the =8- device in a state where the dissolved oxygen concentration is sufficiently high. When automatic control is selected, 81 in the figure is turned on, current flows through the normally closed switch CR10 to the coil CR9-, the normally open switch CR9 is turned on, and the normally closed switch CR8 is turned on.
-1, Normally open switch x 1 through CR3
A voltage is applied to. At this time, if the dissolved M-concentration is above the limit value, relay x1 is turned on, and current flows through the coil 1-Rl- and the coil CR1 of the timer TR1. Since current flows through the coil CR1-, the normally open switch CR1- is turned on, so even if the relay x1 is turned off after this, the coil CR1- and the tin A current continues to flow through the current of TR1 and is self-maintained.

] When current flows through the coil CR1-, the normally closed switch CR1 is turned off. Prior to this point,
Since the switch TR2 is turned off after the set time has elapsed, no current flows through the coil CR5-, and the normally open switch CR5' is turned off, so the coils CR4-1+, CR4-2', No current flows through TR2-. ] Normally open switches CRI-1' and CR4-12 are
is off.

When CR4-1' is turned off, no current normally flows through coil CR8-2-, as described later, and CR8-2 is turned off, disconnecting the select switch from the motor control device and causing the motor to stop. is not started.

(2) Next, timer relay TR1- starts operating from this state, and when the first set time (for example, 2 hours) has elapsed, switch TR1 is turned on and current flows through coil 0R2-. Then the normal open switch CR2'
, CR22 and CR23 are turned on. switch C
When R21 is turned on, no current flows through the coil CR5 as described above, and the normally closed switch CR
5 is on, the current continues to flow through the switch CR2'', and the normally open switch CR2' remains on regardless of the state of the switch T'R1. On the other hand, the normally open switch CR23 is turned on. Then,
Current flows through coil CR3''', normally closed switch CR3 turns off, and coils CR1- and TR
Cut off the current flowing to 1”.

When the current flowing through the coil OR1 is cut off, the normally closed switch CR12 is turned on. At this time, when the dissolved oxygen concentration reaches the preset lower limit value, relay Y1 turns on, so normally open switch CR
Coil CR4-1-1CR1-2, TR2 through 22
- Current flows through. When current flows through the coil CRI-1-, the normally open switch CRI-13 is turned on, and the current flowing through the coil 0R4-1- is self-maintained.

On the other hand, the normally open switch CR4-1' is also turned on, and the motor is started from this point on.

(3) Next, if the dissolved oxygen concentration falls below the lower limit before the first set time elapses, =11- At this time, relay Y1 is turned on, but since current is flowing through coil CR1, it is normal. Closed switch CR
12 is turned on, and the normally open switch CR5' is also turned off.
No current flows through the coils CR4-1, CR4-2, and timer TR2. Therefore normally open switch CR4
-1' remains off, and as mentioned above, normally open switch CR8-2 is normally off, so
The connection between the select switch S1 and the motor control device remains disconnected, and the motor is not started. That is, feedback control of the aeration amount is not performed on the lower limit side of the dissolved oxygen concentration.

This is because the temporal change in dissolved oxygen concentration is originally small on the lower limit side, so the wastewater concentration does not change either with feedback control or on/off control using a timer, and on/off control has the effect of reducing the number of motor operations. This is because they have

12- (/I) Next, consider the state (2) above, that is, the time when the motor is started and aeration is started.

From this point on, the timer TR2- is energized, so the switch TR2 is turned on, no current flows through the coil CR5'', and the normally open switch CR5' is turned on. Therefore, the energization to the timer relay TR2'' is self-maintained. At the same time, energization of the coils CR11'' and CR4-2'' is also maintained. Therefore, from this point on, during the second set time (for example, 20 to 30 minutes) set by timer TR2, the dissolved oxygen concentration exceeds the upper limit and relay x1 is turned on as shown in (1) above. Next, energize TR1', C
Even if RI- is energized and -Marc closed switch CR12 is turned off, current continues to flow to coils CR4-1+ and CR4-2-, and the motor continues to operate. This results in
Even if a temporarily high dissolved oxygen concentration is detected due to air bubbles hitting the dissolved oxygen meter, it is possible to prevent the motor for the blower 3 from malfunctioning and stopping. Therefore, hunting is prevented.

When the timer relay TR2 is turned off after the second set time has elapsed, current no longer flows through the terminal CR5-, and the normally open switch CR5' is turned off. Therefore, after this, when the dissolved oxygen concentration exceeds the lower limit and the normal open switch CR12 turns off as described above, the coil C
No current flows through R/I-1', CR4-2-1TR2-, the normally open switch CR4-1' is turned off, and the motor operation is stopped. That is, feedback control is performed on the dissolved oxygen concentration upper limit side, and the wastewater concentration can be accurately controlled within a specified value.

(5) Next, other circuits will be explained.

0MO2 and 0MO3 are relays that turn off when the motor current exceeds a specified value. (Since there are two motors, they are connected in series.) When this relay is turned off, the coil CR6 is no longer energized, the normally open switch CR6 is turned off, and the power to the timer TR3 is cut off.

When a third set time (for example, 3 hours) has elapsed from this state, timer relay TR3 is turned on and abnormality indicator lamp R is turned on. (The lighting status of the abnormality indicator lamp R is the same as that of coil CR7- and normally open switch C.
Self (S< held by R7', push button P[3
It will not be canceled until 2 is changed to Δ). ) Therefore, in the event of an abnormality, recovery must be done manually.

In addition, if one of the motors is normal at this time, the normally closed switches 51XO2 and 51
At least one of XO3 is on and coil C
Power is applied to R7- and normally open switch CR72
When turned on, current flows through Lucille CR8-1, CR8-2', normally open switch CR8-2 is turned on, and a normal motor is forced to operate.

(6) Also, timer relay TR4 and
'' is for automatic reflex 1~ when power is restored, and TR4 is turned on for a certain period of time after power is restored, and blower 3 is turned on automatically if the dissolved acid concentration is below the limit value. It is for the purpose of

As described above, according to this embodiment, the following effects can be obtained.
I'm happy.

First, the dissolved oxygen concentration in the aeration tank 3 can be reliably controlled within a predetermined range between the lower limit value and the lower limit value.
It is possible to prevent excessive amounts of dissolved oxygen in the water.
H) can be further stabilized.

Further, even when the inflow water stops, it can be easily and automatically covered, furthermore, it is possible to prevent hunting after starting the blower 3, and it is also possible to cope with the power outage.

Further, the control device 6 and the dissolved oxygen meter 4 can be installed in a small space, and a predetermined amount of dissolved oxygen can be controlled by simply adding a circuit, so that major modification of the existing device is not required.

Furthermore, the number of times the blower 3 is operated can be reduced, especially when the inflow of water has completely stopped, such as at night, resulting in an energy saving effect.

=16-

[Brief explanation of the drawing]

FIG. 1 shows activated sludge treatment 1 according to an embodiment of the present invention! I! FIG. 2 is a block diagram of the device; FIG. 2 is a circuit diagram of the expansion rl+ section and comparison section of the control device shown in FIG. 1; FIG. 3 is a circuit diagram of a backup circuit of the control device shown in FIG. 1. 1... Aeration tank 3... Blower 4 as an air supply means...
... Dissolved oxygen amount 5 ... Detection end 6 ... Control device 7 ... Central part of the state 8 ... Comparison section 9 ... Control section 10... Backup circuit 11... Existing control circuit

Claims (4)

[Claims] (1) In an activated sludge treatment equipment equipped with an aeration tank for storing sewage and an air supply means for supplying air to the aeration tank, the aeration tank is provided with a dissolved oxygen meter for detecting dissolved oxygen in the sewage. , a signal from the dissolved oxygen side is input, and when the signal exceeds a preset upper limit value of the dissolved oxygen concentration, an operation-off signal is output to the air supply means, and the dissolved oxygen concentration is adjusted to the preset dissolved oxygen concentration. An activated sludge treatment apparatus characterized in that a control device is provided which outputs an activation signal when the lower limit of 1 is reached. (2) The activated sludge treatment apparatus according to claim 1, wherein the control device is provided with a timer circuit to keep the air supply means turned on for a certain period of time. (3) The control device is provided with a timer circuit that forcibly turns on the air supply means if the air supply means is not turned on for a certain period of time after the air supply means has been turned off. The activated sludge treatment equipment described. (4) Said control'! 2. The activated sludge treatment apparatus according to claim 1, wherein the AM is provided with means for switching between the AM and the operation control device for the air supply means based on an existing timer setting.