JPH03284398A - Water quality controller for activated sludge process - Google Patents

Abstract

PURPOSE:To stabilize the water quality in an activated sludge process by obtaining the command for the amt. of air to be blown into an aeration tank or the command for the dissolved oxygen concn. based on the measured values of the oxidation-reduction potentiometer(ORP) and pH meter and controlling the amt. of air to be blown into the aeration tank. CONSTITUTION:A fuzzy controller 5 is provided with a means for fetching the measured values of the ORP 3 and pH meter 4 and normalizing the values in the interval between -1 and +1, a fuzzy rule group and a fuzzy inference part. The command for the air amt. is inferred by the fuzzy rule group based on the measured values from the ORP 3 and pH meter 4. The command for the inferred air amt. is inputted to an air amt. control part 6, and a blower is controlled. Accordingly, even when one of the factors of the pH or ORP is affected, for example, by an interfering ion and the relation to nitrification is broken, the controller is hardly disturbed. The pH value is not deviated from the appropriate range, and the nitrification process is stably controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a water quality control device for an activated sludge process.

B9 Summary of the Invention The present invention is an apparatus for controlling the degree of nitrification of a treated liquid in an activated sludge process, in which an oxidation-reduction potential meter and a pH meter are provided in an aeration tank, and based on these measured values, the amount of air blown or dissolved By determining the target value of oxygen concentration, the nitrification process can be managed stably.

C9 Conventional technology When controlling an activated sludge process, conventionally, as shown in Figure 3, a target value and a state quantity are compared, and a control command is output from a PID controller to the activated sludge process based on the comparison result. was. The control method shown in Figure 3 is also used to manage the nitrification process of the treated liquid obtained by activated sludge treatment, in which the amount of air blown is adjusted by a PID controller by comparing the target value and the measured value of the oxidation-reduction potential. ing. It is known that stable management of the nitrification process not only stabilizes nitrification, but also stabilizes the BOD concentration and pH value of treated water, and is also important from the perspective of energy conservation. Regarding the measurement of the nitrification process, for example, a redox electrometer is used as a substitute because there is no automatic measuring device that can continuously measure the nitrification process.

D0 Problems to be Solved by the Invention However, the relationship between the redox potential and the degree of nitrification is strongly nonlinear, and the relationship is likely to change. For example, if nitrification progresses too much, the pH
The values sometimes deviated from the appropriate range, and as a result, the quality of the treated water was unstable.

An object of the present invention is to stabilize the water quality of activated sludge.

21 Means for Solving the Problems The present invention provides an oxidation-reduction potential meter and a pH meter installed in an aeration tank.
a means for determining a target value for the amount of air blown into the aeration tank or a target value for dissolved oxygen concentration in the aeration tank based on the measured values of the oxidation-reduction potentiometer and the pH meter, and a target determined by this means. The air blowing amount control section controls the air blowing amount into the aeration tank based on the value.

F1 action: For example, at a predetermined timing, fuzzy inference is executed based on the measured values of oxidation-reduction potential and pH, and the degree of nitrification at that time is estimated, and a corresponding target value for the air flow rate is inferred, and this target value is determined. Control the amount of air flow.

G. Embodiment The present invention will be explained using fuzzy inference as an example. In Figure 1, 1 is an aeration tank in the activated sludge process, 2 is an aeration pipe, and 3 is an oxidation-reduction potential (rORP).
4 is a pH meter, 5 is a fuzzy controller, and 6 is an air flow rate control unit including a blower and the like.

The fuzzy controller 5 includes means for taking in each measured value of the ORP meter 3 and the pH meter 4 and normalizing it into an interval of =1 to +1, a fuzzy rule group, and a fuzzy inference section that executes fuzzy inference. ing.

For the measured value of ORP, for example, θ ~ 300 mV -
Normalized to the interval l~+1, for the measured pH value,
For example, 5.0 to 8.0 is normalized to an interval of =1 to +1.

The fuzzy rule group is based on the measured values from ORP total 3 and p
This is a set of rules for inferring the target value of the air blow amount based on the measured value from the H total 4, and is expressed in a matrix format as shown in the table below, for example.

(The following is a margin) However, x and y are values obtained by normalizing the pH value and ORP value, respectively, and U is a membership value corresponding to the target value of the air flow rate. Further, the first row and first column in the table correspond to the condition part of the rule, and the intersection of the vertical and horizontal columns corresponds to the conclusion part of the rule. For example, if you combine the first row and first column of Table 1, if x=NB and y-PB the
The rule is n u=NB. PB (positive and large),
NB (negative and large) etc. are fuzzy labels, and membership functions shown in FIG. 2 are assigned to them. Such a rule is based on researching the relationship between the ORP value, pH value, and degree of nitrification in advance, and then using that data. It is created based on this.

Next, the operation of the above embodiment will be explained. It is assumed that wastewater flows into the aeration tank 1 from an inflow channel (not shown), and air is supplied here from the aeration pipe 2 to aerate the mixed liquid of wastewater and activated sludge.

The measured values of the ORP meter 3 and the pH meter 4 are input to the fuzzy controller 5, where they are normalized.

The fuzzy controller 5 calculates the normalized measurement values x, y
A fuzzy rule is applied to, for example, the Mamdani method to infer the target value of the air flow rate. Specifically, for one rule of the rule group shown in the matrix table above,
Apply the value of to the corresponding membership function in the conditional part, find the smaller membership value among the obtained membership values, cut the membership function in the conclusion part with this value, and repeat these trials for all rules. The cut lower part of the membership function in the conclusion part is superimposed on all the rules, and the centroid value of the union is used as the inference value.

The target value of the airflow amount inferred in this way is input to the airflow amount control section 6, and the blower is controlled here so that the airflow amount becomes the target value.

In the present invention, when inputting the measured values of ORP and pH, the values of ORP and pH are sampled at a predetermined timing, and the difference from the previous sampling value is calculated for each, and the change is also taken into consideration. Alternatively, the target value of the airflow amount may be inferred. In this case, the condition part of the fuzzy rule includes ΔX and Δy in addition to x and y.

Further, the target value of the airflow amount to be inferred may be a set value of the airflow amount, or may be a change from the current airflow amount.

Furthermore, in the present invention, instead of inferring the amount of air flow.

(Dissolved oxygen) concentration may be inferred, in which case the DO concentration set value or the change in the Do concentration is taken as the target value.

In the above, it is desirable to set an upper limit value and a lower limit value for the target value of the air flow rate or Do concentration so that the target value does not deviate from the limit value.

In the present invention, the method for determining the target value is not limited to fuzzy inference, but if fuzzy inference is used, it is possible to appropriately control nonlinear relationships such as the degree of nitrification and ORP, and management based on the experience of experts. I can do it.

H1 Effects of the Invention According to the present invention, focusing on the fact that the nitrification process has a strong correlation with both pH and ORP,
The amount of air blown is controlled by predicting the degree of nitrification based on the measured values of both. Therefore, even if one of the factors, pH or ORP, is affected by interfering ions and the relationship with nitrification is disrupted, this will not directly affect the obtained target value of air flow rate or target value of Do. , it becomes less susceptible to disturbances, there is no fear that the pH value will deviate from the appropriate range, and the nitrification process can be managed stably.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a graph showing a membership function, Fig. 3 is a block diagram showing a conventional example, 1...Aeration tank, 3...ORP meter, 4...pH meter,
5... Fuzzy inference section, 6... Air flow rate control section. 2 people outside

Claims (1)

[Claims] (1) A redox potential meter and a pH meter installed in the aeration tank, and based on the measured values of these redox potential meter and pH meter, the target value of the amount of air blown into the aeration tank or the dissolved amount in the aeration tank. Water quality for an activated sludge process, comprising means for determining a target value of oxygen concentration, and an air flow rate control unit that controls the air flow rate into an aeration tank based on the target value determined by the means. Control device.