JPS60179195A - Method for controlling do in aeration vessel to fixed value by feedforward control - Google Patents

Abstract

PURPOSE:To control precisely the DO value in an aeration vessel to a fixed value by agitating a fixed amt. of original water to be treated which is supplied into the aeration vessel and a fixed amt. of sludge taken from a settling vessel for specified hours, and measuring oxygen consumption during said hours. CONSTITUTION:The flow rate of the original water 2 to be treated which is charged into an aeration vessel 1 is measured by a flowmeter 22, and the detected value is inputted to a controller 21. The amt. of aeration air is obtained by the controller 21 on the basis of said inputted value and oxygen consumption. The obtained amt. of aeration air is inputted to an inverter 23 as an electric signal from the controller 21. The number of revolutions of a blower 7 is controlled by the output signal of the inverter 23 to obtain said amt. of air to be needed for aeration. Namely, the number of revolutions of the blower 7 is controlled by feedforward control so that the amt. of aeration air may be regulated in accordance with the BOD load of the original water 2 to be treated which is being supplied into the aeration vessel 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for controlling the DO value (dissolved oxygen amount) in an aeration tank when treating wastewater by an activated sludge treatment method. It can be used in the field of pollution prevention.

Conventional technology The activated sludge method is known as a method for treating organic wastewater such as domestic wastewater, and this method involves aerating the wastewater to be treated by pumping air into the wastewater to oxidize and decompose pollutants using activated sludge. This is a method in which activated sludge is separated by precipitation and the clean supernatant is discharged. Therefore, in this method,
According to the BODif of the wastewater to be treated, that is, B
It is necessary to perform aeration using foot pressure (according to the OD load). Conventionally, the Do value (dissolved oxygen amount) in the aeration tank was set in advance to prevent a decrease in purification ability and unnecessary energy consumption. It is controlled to maintain a constant value.

In other words, in activated sludge treatment, activated sludge consumes oxygen dissolved in wastewater to decompose pollutants, so if the amount of dissolved oxygen is too low or almost zero, activated sludge activity will stop. If the amount of dissolved oxygen is increased beyond the maximum amount consumed by activated sludge, the power required for aeration will be consumed unnecessarily. Therefore, in order to perform efficient processing, it is necessary to control the aeration air volume so that the Do value is kept at a predetermined constant value.

FIG. 1 is a schematic diagram showing a conventional DO constant value control system in aeration 4n, in which raw water to be treated 2 and return sludge 5 extracted from a settling tank 3 via a pump 4 are supplied to the aeration 01, In addition, by blowing air into the mixed liquid 6 in the mouth air tank 1 with a blower 7, it is carried out all at once. The Do of the mixed liquid 6 is measured by a process Do meter 8, and its output signal is input to a controller 9, where signal processing and comparison P1, etc. are performed, and the results are input to the next stage inverter 10. At the same time, inverter 10
The rotation speed of the blower 7 is controlled by the output signal of the blower 7. In other words, when the Do value decreases, the blower 7
The number of rotations of the blower 7 is increased to increase the number of aeration air ports, and conversely, when the Do value becomes high, the number of rotations of the blower 7 is lowered to reduce the amount of aeration air 9.

Conventionally, Do constant value control in the aeration tank 1 is performed by feedback control, and the Do value fluctuates according to increases and decreases in the BOD load of the raw water to be treated 2, so in the end, the aeration 0 is adjusted according to the BOD load. It can be increased or decreased.

However, in the conventional method described above, the D
Since the aeration air volume is changed after the o value increases or decreases, there is a large delay in control time, and therefore, if the BOD load of the raw water to be treated 2 fluctuates greatly, the aeration 41
A problem arises in which the variation between the Do value and the target value within 1 becomes large. In such a case, since the processes of aeration, precipitation, and discharge are carried out continuously, there is a risk that wastewater with a high BODn degree will be discharged.

Purpose of the Invention This invention was made in view of the above circumstances, and is capable of precisely controlling the Do value in the aeration tank to a constant value even when the SOD load of the raw water to be treated varies greatly. The purpose is to provide fixed price control method payment.

Structure of the Invention The present invention involves stirring and mixing a certain amount of raw water to be treated to be supplied to an aeration tank and a certain amount of activated sludge extracted from a settling tank for a predetermined period of time, and measuring the amount of oxygen consumed during that time. 1
This system is characterized in that the aeration air q in the aeration tank is controlled based on measured values.

Example The present invention will be explained below based on examples.

First, to explain the apparatus, FIG. 2 is a diagram showing an apparatus for carrying out the method of the present invention, in which the same members as those in the apparatus shown in FIG. The device shown in 2 is configured to measure the amount of oxygen consumed by activated sludge treatment for a certain period of time as a substitute value for the BOD concentration of the raw water to be treated 2, and to control the aeration interval based on the measured value. . That is, the oxygen consumption measurement container 11 has a drain valve 12 at the bottom, a porta-pull DO meter 13 inserted from its upper end, and a stirrer in a magnetic stirrer 14 inside the measurement container 11. 15 are accommodated. Furthermore, the raw water head tank 16 is communicated with the measurement container 11 via the raw water injection valve 17, and the sludge head tank 18 is communicated with the measurement container 11 via the sludge injection valve 19. Then, the raw water head tank 16 [here, the raw water 2 to be treated is pumped up by the raw water sampling pump 20, and the sludge head tank 18
In this case, a part of the returned sludge is pumped by the pump 4 (3).

Further, while the portaple Do meter '13 is connected to the controller 21, the flow meter 22 which measures the flow 0 of the raw water to be treated 2 is electrically connected to the controller 21 in order to input the measurement result to the controller 21. It is connected. I131711 device 21
is connected to an inverter 23, and the number of rotations of the blower 7 is controlled by the output signal of the inverter 23 using a frequency conversion method.

Next, to explain in detail the present invention using the above-mentioned device, the raw water 2 to be treated is pumped up to the raw water head tank 16 by the raw water sampling pump 20, and a part of the return sludge 5 is supplied to the sludge head tank 8. Keep it
In this state, the raw water injection valve 17 and the sludge injection valve 19 are each opened for a predetermined time to feed a certain amount of the raw water 2 and sludge 5 into the measuring volume 'AN 11 Tr'Z. After that, the magnetic stirrer 14 is started to stir the liquid mixture in the measuring container 11, and at the same time, the DO value is measured for a predetermined period of time using the portable DO meter 13, and after the measurement is completed, the drain valve 12 is checked and the C measurement is performed. The mixed liquid in the container 11 is discharged. Then, by subtracting the DO value at the end of the measurement from the DO value during most of the measurement, the raw water to be treated 2 supplied into the measurement container 11 is
And the oxygen consumption R within the certain period of time for a certain amount of sludge 5 is calculated. This kind of Entaku has a total of 1 Portaple DO.
3 is input to the conventional controller 21, and at the same time, the flow rate of the raw water to be treated 2 to the air tank 1 is measured by the flow meter 22, and the measured value is transmitted to the controller 21. The controller 21 determines the required amount of positive air air based on the input value and the above-mentioned nine element consumption values. The thus determined aeration air volume is inputted from the controller 21 to the inverter 23 as an electric signal, and the rotation speed of the blower 7 is controlled by the output signal of the inverter 23 so that the above-mentioned required exhalation l111fit is achieved. . That is, the number of revolutions of the blower 7 is controlled in a feedforward manner so that the air flow rate corresponds to the BO'D load of the raw water 2 to be treated that is being supplied to the aeration tank 1.

Therefore, by automatically performing the measurement operation of the oxygen consumption n described above using a timer, etc., and by performing the feedforward control of the rising and falling air, including the measurement of the oxygen consumption amount, at regular intervals, the volume of positive airflow can be increased. The suspension can be set at any time to match the BOD load of the raw water to be treated 2, and as a result, the Do value within 11 can be maintained at a constant value.
The Do value of the mixed liquid 6 in the aeration 411 is the process Do total 8
Continuously measure by

Effects of the Invention As is clear from the above explanation, according to the method of the present invention, a certain angle of the raw water to be treated to be supplied to the aeration tank and a certain amount of activated sludge extracted from the settling F2 tower are determined in advance. Stir and mix for a predetermined period of time, and measure oxygen consumption during that time.
Since the aeration ff1m in the aeration tank is controlled based on the obtained measurement value, the air volume can be set according to the BOD load of the raw water to be treated that is being supplied to the aeration tank.In other words, the control time is delayed. There is almost no BO of raw water to be treated.
Even in cases where the D load fluctuates greatly, the viscosity can be controlled with good viscosity so that the DO value becomes the target value. In addition, in this defense method, since the control target value of 0 is good, the control target value of the Do value can be brought close to the theoretical value, and as a result of (a), there is no need to allow for a margin in the aeration air, so the blower
It is possible to reduce the driving energy to the minimum necessary and save energy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram schematically showing a conventional Do constant value control system, and FIG. 2 is a schematic diagram schematically showing an apparatus for implementing the method of the present invention. 1... Aeration tank, 2... Raw water to be treated, 3... Sediment Y1 tank, 5... Activated sludge, 7... Blower-111
...Oxygen quencher, i-static container, 13... Portable DO meter, 14... Magnetic stirrer, 1
6... Raw water head tank, 17... Raw water injection valve,
18... Sludge head tank, 19... Sludge injection valve, 21... Controller, 22... Flow meter, 23...
·inverter. Applicant Toyota Motor City Co., Ltd. Agent Patent Attorney Yutaka 1) Hisashi Take (and 1 other person) Rin 2

Claims (1)

[Claims] After the raw water to be treated is subjected to activated sludge treatment in the aeration tank, the activated sludge is separated by sedimentation in the settling tank. A certain amount of the raw water to be treated is to be supplied to the aeration tank, a certain amount of activated sludge extracted from the settling tank, and Aeration by feedforward control characterized by stirring and mixing for a predetermined period of time, measuring the amount of oxygen consumed during that time, and controlling the aeration in the aeration tank based on the measured value. In-tank Do constant value control method.