JP2909723B2 - Wastewater treatment control method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling the operation of a wastewater treatment method utilizing aerobic microorganisms.

[0002]

2. Description of the Related Art As a wastewater treatment method, a biological treatment method using an aerobic microorganism is a widely used wastewater treatment method. A typical process is an activated sludge treatment method. In addition, the activated sludge treatment method depends on the shape of the aeration tank, the method of injecting raw wastewater and the method of applying load, etc.
Oxidation rich, step aeration method,
There are various variations such as complete mixing. The treatment principle is common, and aerobic microorganisms capture the pollutants in wastewater and obtain oxygen for the supply of oxygen to decompose, thereby obtaining energy for biological activities, and decompose and synthesize pollutants in wastewater. Purification of wastewater by highly concentrating the biological activities of the natural world that maintain and proliferate their own organisms. Therefore, whether wastewater can be treated efficiently and cleanly depends on how active the aerobic microorganisms are.

[0003] The BOD decomposition rate of activated sludge in the activated sludge treatment can be expressed as follows. When the activity of sludge is defined as the ability of a unit amount of activated sludge to decompose BOD in a unit time when supplied with an appropriate amount of BOD substance and oxygen, BOD decomposition rate = f (BOD concentration, dissolved oxygen concentration, ML
SS × sludge activity). Here, BOD is the biochemical oxygen demand, and MLSS is the sludge concentration of the aeration tank mixture.

[0004] For this reason, the operation of the activated sludge treatment is as follows. 1. There is an appropriate amount of decomposable pollutants (= BOD load). 2. Decompose pollutants and supply oxygen required for microbial respiration. It is necessary to ensure the amount of pollutants and the type and amount of microorganisms that are suitable for the substrate, and to create an environment in which microorganisms suitable for each treatment method can easily grow exclusively. As a management index for this: 1. Chemical oxygen demand (COD) as an alternative index of BOD of raw water 2. Dissolved oxygen concentration in the aeration tank (DO value) 3. MLSS value, pH, temperature, salt concentration, etc. The sludge volume index (SV
4. I), MLSS, returned sludge concentration, etc. Indices for managing the state of the treated water include COD, transparency, suspended solids concentration (SS), pH, and the like.

FIG. 1 shows a basic flowchart of a standard activated sludge treatment apparatus. 1 is a raw water pump, 2 is a raw water flow control valve, 3 is an aeration tank, 4 is an aeration blower, 5 is an inverter for adjusting the output of the blower, 6 is a diffuser pipe, 7 is a final sedimentation tank, 8 Is a return sludge pump, and 9 is a return sludge flow control valve. The normal operation of the activated sludge treatment apparatus performs the following operations with reference to the above management index. 1. The raw water control valve is operated to adjust the treated water amount and the BOD load (concentration × water amount) based on the BOD of the raw water, the amount of wastewater to be treated, and the quality of the treated water. 2. The air volume of the aeration blower is adjusted by the inverter based on the BOD load and the DO value to adjust the aeration air volume. 3. The MLSS is adjusted by operating the return sludge control valve based on the SVI and the return sludge concentration. Automatic management of the activated sludge treatment device is theoretically possible if the management index is managed by an automatic analysis instrument or management instrument, and the signal is calculated by a computer to control the above operation amount. Few examples have been put to practical use in operations. The causes can be summarized in the following two points. 1. There is no automatic instrument that can perform reliable measurement in a short time so that the BOD can be directly reflected in driving operation. Automatic instruments that can quickly measure COD, which is an alternative index of BOD, are practically used. However, in actual operation, the BOD of raw water is composed of various components, and the composition and concentration vary greatly.
The value of BOD cannot always be estimated from the value of OD or the like. 2. In an actual operation, the activity of sludge fluctuates under the influence of various factors, but there is no simple means for judging the activity useful for the actual operation. (In theory, it is possible to judge from the operating conditions such as the BOD and DO value that are decomposed and removed in the aeration tank, but it is not possible to obtain a reliable BOD in a short time.) Autonomous driving methods are limited to very specific wastewaters where there is little substrate variation in the wastewater.

As described above, although the need for automatic driving is high, in an actual operation in which fluctuations are severe, it is general that the judgment of the operation amount from the management index depends on the skill of the operator.
If the quality of the treated water such as BOD is constantly maintained at a certain value or less, it is difficult to predict the fluctuation of the wastewater and the fluctuation of the activity of the sludge. This means that the original capacity of the processing apparatus is not sufficiently utilized, and that the power of the aeration blower is wasted.

[0007]

SUMMARY OF THE INVENTION In wastewater treatment utilizing aerobic microorganisms, an automatic operation control method and apparatus for controlling operating conditions by sampling and measuring and analyzing wastewater during or after treatment is developed. By doing
An object of the present invention is to enable labor saving of apparatus operation, stable processing, and energy saving.

[0008]

SUMMARY OF THE INVENTION In wastewater treatment using aerobic microorganisms, wastewater during aeration treatment is sampled, dissolved oxygen (DO1) in the wastewater is measured, and then the inflow of new sampled wastewater is stopped. The change of decreasing dissolved oxygen (DO2 change curve) is measured with oxygen supplied , and then the wastewater is aerated with air to measure the increasing change of dissolved oxygen (DO3 change curve). Or this DO
A liquid containing a known amount of a BOD substance is added to the wastewater instead of the three-change curve, and air is aerated to increase the dissolved oxygen (D)
O3 'change curve), and at least information on sludge activity, untreated BOD concentration, and excess or deficiency of aeration air is specified from the shapes of the DO1 and DO2 change curves and the DO3 change curve or the DO3' change curve. The target sludge activity, the untreated BOD concentration, and the target inspection DO curve pattern are compared with each other, and a control signal and an alarm signal for operating conditions such as an aeration air amount and a processing amount are output.

[0009]

FIG. 2 shows B in an aeration tank of a standard activated sludge treatment apparatus.
It is a schematic diagram which shows the distribution state of OD density | concentration, the dissolved oxygen density | concentration of a liquid mixture, and the amount of aeration air. Since the BOD concentration is high near the inlet of the aeration tank and the oxygen consumption rate for the BOD decomposition of the activated sludge is high, the dissolved oxygen concentration of the mixed solution is usually low even if the amount of aerated air is increased. When the concentration of the BOD that can be decomposed is reduced near the outlet of the aeration tank due to the progress of the treatment, the oxygen consumption rate for the BOD decomposition of the activated sludge decreases, and the dissolved oxygen concentration in the mixed solution increases. Since this change remarkably changes as the BOD concentration decreases, the state of the treatment can be determined to some extent from the change in the dissolved oxygen concentration of the mixed solution near the outlet of the aeration tank.

A detection method for grasping the status of processing according to the present invention will be described. FIG. 3 is a schematic diagram illustrating the present detection method.
One cycle of the detection method includes the following three stages.
The first step is a step of measuring dissolved oxygen in the activated sludge waste liquid in the sampled aeration tank. The second step is a step of measuring the process of decreasing the dissolved oxygen concentration by cutting off the supply of oxygen to the waste liquid. The third step is a step of measuring the process of increasing the dissolved oxygen concentration by re-aeration of the waste liquid.
At this stage, the 3 ′ step of adding a known amount of BOD substance and measuring the process of increasing dissolved oxygen by re-aeration may be used instead of the third step.

The curve in solid line in FIG. 3 shows the change in dissolved oxygen for a typical example. In the first step, the waste liquid in the third step of the previous cycle contained in the measuring vessel is extruded with new sampling waste liquid, and is completely replaced to measure the dissolved oxygen concentration. The measured value DOS1 represents the dissolved oxygen concentration in the aeration tank. The value of DOS1 provides complex information indicating the degree of excess or deficiency of aerated air relative to untreated BOD in relation to sludge activity. The time t1 required for the first step is usually about 3 to 5 minutes, depending on the shape of the sampling container, the flow rate of the sampling liquid, and the like.

In the second step, the flow of new sampling liquid is stopped. Since the dissolved oxygen is consumed by the respiration of the activated sludge in the mixed solution and the decomposition of the BOD, the dissolved oxygen concentration decreases. If the activity of the sludge is good and the BOD substance is sufficient, the dissolved oxygen is rapidly consumed. Conversely, when the sludge activity is low or when the amount of BOD substance is small, the consumption of dissolved oxygen becomes slow and it is difficult to reach 0 ppm. That is, the measurement curve in the second step is composite information of the sludge activity and the untreated BOD. FIG. 4 schematically shows two examples of typical curves in the second step. The curve a is a typical pattern of the former, and the curve b is a typical pattern of the latter. The measurement time t2 of the second step is set to a time necessary and sufficient for detecting the above difference, and usually 7 to 15 minutes is appropriate. However, if the dissolved oxygen concentration in the first step is already low, it will not be effective data, so that the measurement time in the second step can be extremely shortened for the purpose of shortening the measurement cycle time.

In the third step, the end liquid of the second step is re-aerated. FIG. 7 is a schematic diagram for explaining the phenomenon in the third step. The curve g in the figure shows the change over time in the BOD concentration. curve of h represents the temporal change of the dissolved oxygen DO _L. If the activity of the sludge is good and the BOD substance is sufficient, the rate of decomposition of the BOD is determined by the rate of supply of oxygen. The value of DO of this time (DO _L) is expressed by the following equation. _{γ = K L a (DO S} -DO L) ... (1) Equation gamma: the decomposition rate K _L a: overall oxygen transfer coefficient DO _S: saturated dissolved oxygen concentration DO _L: DO _L of dissolved oxygen concentration (1) is It is represented by a straight line portion of a constant value in the oxygen supply rate-limiting region of the curve b. The change in BOD decreases linearly as shown in the same region of the g curve. BOD substances is reduced, the degradation rate of BOD and becomes equal to or less than the C _P in FIG. 7 is affected by BOD concentration, represented by the following formula. Z: Sludge activity The formula (2) is as follows. -z (tt _p ) C = Cp · e (3) On the other hand, the rate at which the DO value rises depends on the total rate of oxygen consumed by the sludge to decompose the BOD and oxygen consumed by the respiration of the sludge, and by aeration. Since it is the difference in the rate of oxygen supplied into the mixture, it is expressed by the following equation. β ₁ , β ₂ : Coefficient MLSS: Sludge concentration in aeration tank V:
The value of DO _L of the mixture amount (4) is mosquito BOD concentration-determining region of the curve h in FIG. 7 - while after t _p as shown in blanking the gentle暫増mosquito - becomes blanking, BOD concentration becomes Bed - mosquitoes which rapidly increases toward the smaller _{(DO S -β 2 · MLSS /} K L a).

The change curve in FIG. 3 is a typical example of a waste liquid having a good sludge activity and a sufficient amount of untreated BOD. The change process is roughly classified into three. Initially, this section is represented by t3a. This section is the section from the consumption of dissolved oxygen in the second step until sludge in an oxygen-deficient state is supplied with new oxygen by aeration and returned to normal, and is usually very short. Time. The following is the section represented by t3b. In this section, sludge decomposes BOD material in the waste liquid, and the dissolved oxygen concentration is decomposed by a value that balances the rate consumed in decomposing BOD substance and the rate of dissolution of oxygen by aeration. As long as there is sufficient BOD material available, the curve will be loose. The last is a section represented by t3c, and this section is a section where the dissolved oxygen concentration rises sharply due to a decrease in the consumption rate of oxygen due to a decrease in the BOD substance. FIG. 5 schematically shows three examples of typical curves in the third step. The car of c
Curve is a curve with a section of t3b clearly,
The substance D was decomposed, indicating that there was untreated BOD and sludge activity was good. The curve of e is a curve which rises rapidly from the beginning without the section of t3b, indicating that there is no BOD substance to be decomposed or the sludge has extremely low activity and consumes very little oxygen. I have. The curve of d is halfway between c and e, and the interval of t3b is not as clear as c. The curve d is a curve which often appears when the measurement point is normally treated near the outlet of the aeration tank and the amount of untreated BOD is small, but the activity of the sludge may be slightly lowered. In such a case, the same curve is obtained, so that the situation is specified by comprehensive judgment with the data in the first step and the second step and the data of the change with time.

Since the curves of d and e in FIG. 5 have a low oxygen consumption rate, the value of DOS1 in the first step must be high. When DOS1 is high, the curve of c does not appear. FIG. 6 shows a typical curve in the third step which is used instead of the third step when the curves d and e are predicted to appear. In the 3 ′ step, a known amount of B
Since the OD substance is added and re-aerated, if the sludge activity is normal in the waste liquid in the situation corresponding to d or e, the t3b section corresponding to the known amount of BOD substance clearly appears as f. . If the t3b section does not appear or is short, it can be specified that the sludge activity is low. Thus the third
The 'step can be used in place of the third step when the identification of the activity of the sludge is unclear in the inspection of the third step, whereby the specific identification becomes possible. B used in the 3 ′ step
As the OD substance, it is best to select a substance capable of easily decomposing the microflora of the activated sludge treatment apparatus, but may be a substance which is generally easily decomposed such as glucose solution.

Whether or not to use the third step instead of the third step can be selected in advance by judging the inspection data of the first and second steps by a computer. In order to specify the sludge activity after analyzing the data obtained by performing the step with a computer, the method of performing the third step again when it is not clear is that the time required for one inspection cycle is as follows. Although it is longer, it is a possible means because much data can be obtained, and does not depart from the method of the present invention.

FIG. 8 is a flowchart showing an example of an apparatus embodying the present invention. Reference numeral 10 denotes a dissolved oxygen meter. Numeral 11 denotes a measuring vessel, in which a sensor of a dissolved oxygen meter is immersed in a sampling liquid in the vessel. The shape of the container is such that the arrangement of the inlet and outlet of the liquid and the accumulation of air do not occur so that the measurement error does not occur due to the dissolution of oxygen from the liquid surface. Reference numeral 12 denotes a sampling pump. 13 and 14 are solenoid valves for selecting a sampling flow path. Reference numeral 15 denotes a gas-liquid separation tank for separating coarse bubbles in the sampling liquid. 16 is an aeration circulation pump, 17 is an ejector, 18 is an air flow control valve, and 19 is an air flow meter. Numerals 16 to 19 denote systems used for re-aeration in the third step. The water is flowed by the aeration circulation pump 16 to suck and agitate air from the ejector 17 to dissolve oxygen. Other means for aeration can be used. 20 is a BOD solution tank, 21
Is a BOD addition pump. 20 to 21 are used when adding a known amount of the BOD substance in the third step. 22
Is a computer. The operation of the inspection operation, the analysis of the measurement data, the command of the operating condition, the alarm and the like of the present invention are all managed by this computer. An ordinary personal computer can be used as the computer used in the present invention. In this embodiment, PC-9801RS manufactured by NEC Corporation is used, and A / D and D are provided in the extended I / O slot. / A conversion board
AD12-16 (98) manufactured by Contec Co., Ltd.
E, PO-32B (98) manufactured by Contec Co., Ltd. was used as a digital output board for driving commands such as pumps.
23 is a relay box. 12, 16, 21, 1
For driving of 3 and 14, the relay is operated by a signal from the computer via the digital output board, and the devices are turned on and off at the necessary timing from the first step to the third (3 ') step. Let it. 24 is a converter of the dissolved oxygen meter. The signal of the 10 dissolved oxygen meters is 4 mA with 24 transducers.
The signal is converted into an analog current signal of 20 mA, converted into digital data by an A / D conversion board of a computer 22, and taken into the computer. The computer outputs D / A conversion board and digital output of control operation signals of aeration air amount, raw water treatment amount and returned sludge amount, and alarm signals of sludge activity abnormality, treatment abnormality and equipment abnormality as a result of the calculation. Output via the board.

FIG. 9 is a flowchart when the operation of the present invention is viewed as the operation of a computer device. Table 1 is a table showing the classification of the treatment state of the mixed liquid sampled at the measurement point 1 in FIG. 2 using a standard activated sludge treatment apparatus.
In the data processing of the flowchart: 1. Eliminate measurement variations in DO value. 2. Approximate the curve with a straight line The characteristic data such as the start value, the length of t3a, t3b, and t3c, the slope, and the final value are collected. In the processing status specifying calculation of the flowchart, based on the processed data, the pattern as shown in the inspection DO curve column of Table 1 is used.
And the meaning of the patterns of the first to third (3 ') steps, the degree of sludge activity targeted at the measurement point 1, the size of the untreated BOD, and the inspection DO curve pattern. The activity of the sludge at the time of measurement, the size of the untreated BOD, and the suitability of the amount of aerated air at the time of measurement are specified as shown in the treatment status column of Table 1 by comparing with the values shown in FIG. In the operation signal and alarm signal output of the flowchart, a judgment is made by adding the past history data and the data of how the processing status has been changed with time by the operation by the processing status specifying calculation, and a table is displayed. The signal of the operation output column 1 is issued. In the case of the sample at the measurement point 1 in FIG. 2, the inspection target DO curve pattern is usually represented by the case N in Table 1.
o2-2 and 1-1 in the case of the measurement point 2. However, the target inspection DO curve pattern, the degree of activity of the target sludge and the size of the untreated BOD are determined by the shape of the apparatus and the measurement point. Location, wastewater substrate and its fluctuation, required quality of treated water,
It changes depending on the past processing history, future load prediction, etc., and is set manually according to the situation or automatically set by the computer based on various data. For the sake of explanation, Table 1 shows a logic for dividing the first step into three patterns, the second step into two patterns, and the third (3 ') step into three patterns in a total of 14 patterns. Although the method has been shown, in practice it is better to classify more finely, the first step is 5 patterns, and the second step is 4 patterns.
The third and third (3 ') steps are preferably about 5 patterns. Although the contents of Table 1 are qualitatively described for the sake of explanation, they are replaced with quantitative numerical values in the processing in the computer.

[0019]

[Table 1]

As described with reference to FIG. 2, by measuring the dissolved oxygen concentration of the mixed solution near the outlet of the aeration tank, when the sludge activity is good and there is no change, the excess of the untreated BOD and the amount of aerated air is obtained. Insufficient relative information is obtained. Maintaining the dissolved oxygen concentration in the range of 1 ppm to 3 ppm is not sufficient to guarantee the quality of the treated water, but is a necessary condition, and waste of power due to overaeration can be prevented. Therefore, for the purpose of energy saving, a method of measuring the dissolved oxygen concentration in an aeration tank, which has been sometimes performed by the activated sludge treatment method, and controlling the amount of aerated air so that the value becomes a set value (hereinafter referred to as dissolved oxygen) The method will be described while clarifying the difference from the system of the present invention. FIG. 10 is a flowchart of the dissolved oxygen concentration setting method. 25 is a dissolved oxygen concentration meter, 26 is a converter, and 27 is a controller. Generally, the distribution of the aerated air amount, BOD concentration, and dissolved oxygen concentration in the aeration tank in the standard activated sludge method is as shown in FIG. That is, since the BOD concentration in the activated sludge mixture is high near the inlet of the aeration tank, the consumption rate of oxygen required for decomposition is large, and the value at which the dissolution rate and the consumption rate of oxygen are balanced even when the amount of aerated air is increased is 1 ppm or less. It is about. While the BOD concentration in the aeration tank is high to some extent, the value at which the dissolution rate and the consumption rate of oxygen are balanced gradually increases, but remains at a low level. As the BOD substance decomposes near the outlet of the aeration tank, the BOD concentration decreases and the decomposition rate of the BOD substance decreases, so the consumption rate of oxygen decreases, and the value that balances with the oxygen dissolution rate increases significantly. I will do it. In the dissolved oxygen concentration setting method, the dissolved oxygen concentration near the outlet of the aeration tank where the dissolved oxygen concentration changes greatly as shown at the position of measurement point 1 in FIG. The signal is used as a control signal by the controller 27, and the blower 4 is controlled by the inverter 5 so that the dissolved oxygen concentration becomes the set value, thereby saving energy. For example, as shown in FIG. 2, if the untreated BOD increases at the measurement point due to an increase in the BOD concentration by ΔBOD, the dissolved oxygen concentration changes from the value of DO1 in FIG. 2 to the value of DO2. The BOD decomposition rate is increased by increasing the amount of oxygen by increasing the amount of aerated air by Δair. In this way, if the BOD load to be treated in the aeration tank is constant or the change is sufficiently slow, and if the sludge activity is constant or the change is sufficiently slow, the situation of the BOD treatment corresponds to the aeration air amount. The dissolved oxygen concentration setting method also has a function as an automatic control device for ensuring the quality of the treated water, and competes with the product of the present invention.

However, in actual operations, there are rare cases where the BOD load is constant or the change is sufficiently slow, and the sludge activity is constant or the change is sufficiently slow. Even in the raw water storage tank, fluctuations in the load of wastewater, the activity of the substrate and the sludge are still severe even if the water is made uniform. FIG. 11 shows the behavior of the dissolved oxygen setting method in the case where only the sludge activity is varied and the load of the wastewater is constant for simplicity, as indicated by the solid curve.
Zone 1 in FIG. 11 shows a case where the sludge activity is good and constant. In this case, the treated water quality is also controlled to the target value by controlling the DO concentration at a constant value as described above. Zone 2
When the activity of the sludge decreases, the amount of BOD decomposed decreases, the oxygen consumption rate decreases, and the quality of the treated water decreases, but the DO value increases contrary to normal. For this reason, the control signal tends to decrease the amount of aerated air, and tries to return the DO value to the set value by reducing the amount of aerated air. When the activity of the sludge recovers as the zone 3 recovers, the oxygen consumption rate recovers, the DO value decreases, and the amount of aerated air increases. Since the amount of aerated air has been reduced to the level, the state of insufficient air volume is not easily eliminated, and the quality of the treated water continues to deteriorate due to the lack of air volume even in the process of recovering the activity. Even when the zone 4 becomes sludge and the activity of the sludge becomes good, the load of the untreated BOD is added to the normal load. Do not return to level. In actual operation, hunting is further increased because a variation in load is added in addition to the variation in sludge activity. When there is such a fluctuation, the dissolved oxygen setting method does not become an automatic control method for securing the treated water quality.

The operation of the present invention will be described.
In the present invention, as information on the treatment, as described above, the sludge activity, the untreated BOD, and the relative excess / deficiency data of the aeration air amount are described.
Data is obtained. When the activity of the sludge in the first zone is good,
The measured dissolved oxygen concentration curve is as shown by p in FIG. At this time, since a command is issued from the computer to control the DO concentration to a set value, the operation is the same as that of the dissolved oxygen setting method. The dissolved oxygen concentration curve measured when entering the second zone is as shown by q in FIG. Since information indicating that the sludge activity is degraded is included in this curve, even if the DO value deviates from the set value, a command to immediately reduce the amount of aerated air is not issued, and the raw water treatment amount is reduced. Alternatively, a signal is sent to reduce the amount of returned sludge and extend the residence time.
In the case where the decrease in the activity is so large that the DO value becomes too large as shown by the dotted line of j in FIG. 11, the amount of aerated air is reduced as shown by the dotted line of m in FIG. 11 to prevent the DO value from becoming too large. . In the example of FIG. 11, the normal setting value of DO is 2 pp
About m is appropriate, and about 2 ppm is acceptable in the second zone. Therefore, at the end of the second zone, as shown by the dotted line of j, the DO value is higher than the solid line of i in the case of the dissolved oxygen setting method, and the amount of aerated air is considerably reduced in the dissolved oxygen setting method for a long time. On the other hand, in the present invention, the processing speed of BOD is generally increased by the activity of microorganisms in a small area and the normal part, and the degree of deterioration of treated water quality is indicated by the solid line of n in the case of the dissolved oxygen setting method as indicated by the dotted line o. Less than. When the activity of the sludge is restored to the third zone, the consumption rate of oxygen increases. However, since the amount of aerated air is not narrowed down originally, there is no shortage of oxygen, and the treatment is performed with the activity of the sludge. Proceed with recovery. In the fourth zone, since the sludge activity is good, the DO value is controlled to be the set value. In the present invention, since the amount of air is not so narrowed in the second and third zones, the accumulation of residual BOD due to the shortage of air in the integration is small. As shown by the dotted line, the recovery of the treated water quality is earlier than the solid line of n in the dissolved oxygen method.

In the above example, the case where the BOD load does not change has been described. Among the activated sludge treatment methods, in the complete mixing method, the situation in the aeration tank is the same, so that even if the BOD load fluctuates, there is no time delay from the measurement point, so that the above example can be sufficiently controlled. However, in the standard activated sludge method or the step aeration method, it takes a long time for raw water to enter and exit from the aeration tank, and there is not much mixing in the flow direction. Judging the entire inside of the aeration tank is dangerous when the BOD concentration of the raw water and the substrate vary greatly.

Next, the operation when the fluctuation of the BOD load amount is large will be described. For the sake of simplicity, the sludge activity shall not change. When the DO measurement point is measurement point 1 in FIG.
In the case of the standard activated sludge method, the residence time difference from the vicinity of the aeration tank entrance is usually about 5 to 15 hours. In the case of highly fluctuating and unpredictable irregular fluctuating wastewater, measurement point 1
The measurement data in the above reflect the results of the history of the processing status from the past to the present until the measurement point 1 after entering the aeration tank. It is impossible to determine the overall operating conditions. In extreme cases,
If the change in the load is opposite to the operation signal for the amount of aerated air, the quality of the treated water largely hunts. In the present invention, the problem can be solved by performing the DO measurement at two points near the normal aeration tank outlet and near the aeration tank entrance. A case in which measurement is performed at two points, measurement point 1 and measurement point 2 in FIG. 2, will be described.
The data at the measurement point 1 is as described above. A typical example at the measurement point 2 is shown in Case No. 1-1 in Table 1. The value of DOS1 in the first step is B near the aeration tank entrance.
DOS1 is usually 1 ppm or less in the case of a normal processing state where the consumption rate of oxygen is large due to the large amount of OD. Therefore the second
Since valid data cannot be obtained in the step, the process shifts to the third step in about one minute at t2. In the third step, the curve of FIG. From the information of the first step and the third step, the processing status at the measurement point 2 can be specified. The situation at measurement point 2 is measurement point 1 after the elapse of the residence time.
Data. Therefore, the output of the driving operation from the computer becomes more appropriate data by correcting the information from the measuring point 1 with the information from the measuring point 2. Of course, if abnormal data is obtained in the first step, the second step, the third step and the like are applied. These decisions are made automatically by computer software.

The measurement at two locations can be performed by using the flowchart shown in FIG. 8 in terms of the apparatus. When the solenoid valve 13 shown in FIG. 8 is opened, the liquid at the measurement point 1 and the solenoid valve 14 are opened. The pipe may be opened so that the liquid at the measurement point 2 can be sampled when opened. Also, one measurement time is from 20 minutes to 30 minutes from the first step to the third step, so that even if the measurement points 1 and 2 are alternately inspected, more than one measurement data can be obtained per hour. There is no practical problem compared to the length of the residence time. This method cannot be used in the dissolved oxygen setting method. This is because, in the dissolved oxygen setting method, the DO value at the measurement point 2 in the aeration tank is large in the untreated BOD, so that the amount of change in the DO value is small and the degree of the untreated BOD cannot be determined based on the change in the DO value. .

[0026]

The present invention is particularly effective for various activated sludge treatments, contact oxidation treatments, biological denitrification treatments and the like that mainly use buoyant microorganisms. However, the present invention can be applied in common because even a treatment method mainly using sticky microorganisms includes floating microorganisms. The effect of the present invention is that, since the activity of sludge can be specified, operating conditions such as activated sludge treatment can be appropriately set, and the quality of treated water can be improved and stabilized. In addition, since operations such as data collection of various management indices and changes in operating conditions can be largely automated, the effect of labor saving is great. In addition, the power of the aeration blower is not wasted because the aeration air amount is always automatically controlled to the best value according to the processing situation. The magnitude of this energy saving effect depends on the magnitude of fluctuations in raw water, etc.
Sway case, but generally 30% of blower power
A degree of reduction is possible. Since about 40% to 60% of the operating cost excluding depreciation of equipment and labor cost in activated sludge treatment is the power cost of the blower for aeration, this energy saving effect is large.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a standard activated sludge treatment apparatus.

FIG. 2 is a distribution diagram of a BOD concentration, a dissolved oxygen concentration, and the like in an aeration tank of a standard activated sludge treatment device.

FIG. 3 is a schematic diagram showing one cycle of the detection method of the present invention.

FIG. 4 is a schematic diagram showing a typical pattern of the movement of the DO value in the second step.

FIG. 5 is a schematic diagram showing a typical pattern of a DO value movement in a third step.

FIG. 6 is a schematic diagram showing a typical pattern of the movement of the DO value in the 3 ′ step.

FIG. 7 is a schematic diagram illustrating a phenomenon in a third step.

FIG. 8 is a schematic diagram showing an apparatus.

FIG. 9 is a flowchart for processing by a computer.

FIG. 10 is a schematic diagram of a dissolved oxygen concentration setting method.

FIG. 11 is a schematic diagram illustrating a state of processing in an aeration tank.

FIG. 12 is a schematic diagram showing the movement of the dissolved oxygen concentration of a sample solution.

[Explanation of symbols]

3 Aeration tank 4 Aeration blower
10 Dissolved oxygen meter 11 Measurement container 12 Sampling pump
13, 14 Solenoid valve 16 Aeration circulation pump 17 Ejector
Reference Signs List 20 BOD solution 21 Addition pump 22 Computer

[Table 1]

[Table 1]

[Table 1]

Claims (3)

(57) [Claims] In wastewater treatment utilizing aerobic microorganisms, wastewater during aeration treatment is sampled, dissolved oxygen (hereinafter referred to as DO1) in the wastewater is measured, and then the inflow of new sampled wastewater is stopped. With the supply of oxygen cut off, the decrease in dissolved oxygen (hereinafter referred to as DO2 change curve) is measured, and then the wastewater is aerated with air to increase the dissolved oxygen (hereinafter referred to as DO3 change curve). Measure and determine at least the sludge activity, untreated BOD concentration, and excess or deficiency of aeration air amount from the shapes of the DO1, DO2 change curve and DO3 change curve, and target sludge activity, untreated A wastewater treatment control method, comprising: issuing a signal for instructing or controlling at least an increase or decrease in aeration air amount in comparison with a BOD concentration and a target inspection DO curve pattern. 2. In wastewater treatment using aerobic microorganisms, wastewater during aeration treatment is sampled, DO1 is measured, and a DO2 change curve is measured. Then, a liquid containing a known amount of BOD substance is added to the wastewater. And then aerating the air to measure the increase in dissolved oxygen (hereinafter referred to as the DO3 'change curve). From the shapes of the DO1, DO2 and DO3' change curves, at least the sludge activity and the untreated BOD concentration Identify the information of excess or deficiency of the aeration air amount, compare it with the target sludge activity, untreated BOD concentration and target inspection DO curve pattern, and instruct at least increase or decrease of the aeration air amount. A wastewater treatment control method, comprising issuing a control signal. 3. A wastewater treatment using an aerobic microorganism, means for sampling wastewater during aeration treatment, a measurement container containing a sampling liquid, a dissolved oxygen meter for measuring a dissolved oxygen concentration of the sampling liquid, and Means for flowing and stopping wastewater sampled into the measurement container, means for aerating the wastewater, means for adding a liquid containing a set amount of BOD substance to the wastewater, and DO1, DO2 from the dissolved oxygen meter.
Change curve, DO3 change curve or DO3 'change curve from at least sludge activity, untreated BOD concentration,
Identify information on excess or deficiency of the aeration air amount, compare it with the target sludge activity, untreated BOD concentration and target inspection DO curve pattern, and instruct or control at least the increase or decrease of the aeration air amount. Wastewater treatment control device equipped with a computer device.