JP5467593B2 - Excess sludge automatic extraction system - Google Patents

Description

  The present invention relates to a system for treating various types of wastewater generated in the manufacture of a wide variety of products in each plant, and more particularly to an automatic extraction system for excess sludge in a settling basin of a wastewater treatment system.

  FIG. 13 shows a flow of a general waste water treatment system. The wastewater treatment system includes an adjustment tank 11, an aeration tank 12, and a final sedimentation tank 13. In the adjustment tank 11, the pH and oxygen concentration of the drainage are adjusted. In the aeration tank 12, wastewater is treated by an activated sludge method in which organic matter contained in the wastewater is changed to sludge (sludge) by the power of microorganisms and oxygen. In the final sedimentation basin 13, treated water (clear water) and sludge are separated by natural sedimentation, and surplus sludge is discharged out of the system from the final sedimentation basin 13. Moreover, treated water is discharged into the sea, for example. Part of the sludge is returned to the aeration tank 12 from the final sedimentation basin 13 as return sludge in order to keep the amount of sludge retained in the aeration tank 12 constant.

  FIG. 14 shows a conventional operation management method (excess sludge extraction method) of the final sedimentation basin 13 in the waste water treatment system as described above, and the sludge level is conventionally measured by the photoelectric tube sludge level meter 21. It was done using.

  The phototube sludge level meter 21 is configured such that a buzzer sounds when the phototube reacts at the sludge interface, and when the buzzer sounds, the phototube is manually lowered into the final sedimentation tank 13. By measuring the lowered distance, the sludge level (the distance from the surface of the treated water to the interface between the treated water and the sludge) is measured.

  The operator measures the sludge level, for example, three times a day using the photoelectric tube sludge level meter 21, and determines the amount of surplus sludge to be extracted based on the measured sludge level. Based on the determined withdrawal amount, the operator remotely controls the control valve adjusting means 23 installed at the site from the central control room 22. The control valve adjusting means 23 adjusts the opening degree of the control valve 24 provided in the surplus sludge discharge path with respect to the input extraction amount, and based on the input extraction amount, surplus Sludge is discharged. In this example, the extracted amount is input to the control valve adjusting means 23 through the sequencer 25, and a flow meter 26 for measuring the flow rate of the excess sludge is provided in the discharge path. The flow rate measured by the flow meter 26 is input to the control valve adjusting means 23 and transmitted to the central control room 22 through the sequencer 25.

  In the above, a photoelectric tube type sludge level meter is used for measuring the sludge level. However, in Patent Document 1 and Patent Document 2, as in the case of such sludge level measurement, detection of the accumulation state of the deposit in the liquid is performed. Describes the use of ultrasound.

JP 2007-271376 A Japanese Patent Laid-Open No. 9-192411

  By the way, in the conventional surplus sludge extraction method as shown in FIG. 14, since the photoelectric tube type sludge level meter 21 is used for the measurement of the sludge level, the operator performs the measurement three times a day, for example. The sludge level cannot be constantly monitored. Therefore, the adjustment of the extraction amount is not performed immediately in response to the change in the sludge level, so that there is a problem that proper extraction of excess sludge is impaired. In addition, the operation of measuring the sludge level, determining the amount of excess sludge to be extracted, and remotely controlling the control valve adjusting means 24 from the central control chamber 22 has been a burden on the operator.

  On the other hand, if the method using ultrasonic waves as described in Patent Document 1 and Patent Document 2 is adopted for sludge level measurement and an ultrasonic transducer is installed in the sedimentation basin, the sludge level is constantly measured. It becomes possible to do. However, Patent Literature 1 and Patent Literature 2 are for detecting deposits in the liquid, and are systems that enable, for example, automatic discharge processing of deposits based on the deposit state of the detected deposits. Not.

  In view of such circumstances, an object of the present invention is to provide an automatic excess sludge extraction system that allows continuous measurement of sludge level in a sedimentation basin and that automatically removes excess sludge based on the sludge level. There is to do.

According to the invention of claim 1, the system for automatically extracting surplus sludge in the wastewater treatment system sedimentation basin that separates treated water and sludge emits ultrasonic waves at a predetermined period toward the bottom of the sedimentation basin, An ultrasonic transducer that receives the reflected wave is provided, and a sludge level meter that determines the sludge level of the sedimentation basin from the received reflected wave, and the amount of surplus sludge extracted from the sludge level that is output from the sludge level meter. An extraction amount calculating means; and an adjustment valve adjusting means for adjusting an adjustment valve for extracting excess sludge provided in the settling basin based on the extraction amount ;
Scan Rajjireberu meter, sequential data of the sludge level calculated from the reflected wave, the averaging unit and outputting the averaged, processes the data of the sludge level inputted from the averaging unit withdrawing amount calculating means A data processing unit that outputs to the output unit, the input data input from the averaging processing unit is X (t) (where t is time), and the output data that is output to the extraction amount calculating means is A (t) In this case, when the difference between the immediately preceding output data A (t−1) and the input data X (t) is equal to or greater than a predetermined value, the data processing unit converts the immediately preceding output data A (t−1) to A (t). When the difference is less than a predetermined value,
A (t) = {X (t) -A (t-1)} / N + A (t-1) (where N is a constant)
To calculate and output A (t).

According to a second aspect of the present invention, in the first aspect of the invention, the sludge level meter includes a display unit for displaying the data of the sludge level averaged by the averaging processing unit.

  According to the present invention, it is possible to always measure the sludge level in the sedimentation basin, and the excess sludge is automatically extracted based on the sludge level, thereby reducing the burden on the operator. In addition, safe and stable operation of the sedimentation basin can be realized.

The figure for demonstrating the structure of one Example of the excess sludge automatic extraction system by this invention. The block diagram which shows the function structure of the sludge level meter in FIG. The figure for demonstrating the process of the averaging process part of a sludge level meter. A is a graph showing sludge level data before data processing of the data processing unit of the sludge level meter, and B is a graph showing sludge level data after the data processing. The flowchart which shows the processing flow of a data processing part. The flowchart which shows the detailed process flow of step S1 in FIG. The figure which shows the data processing detail by the processing flow shown in FIG. The figure which illustrated the data processing details of step S4 in FIG. 5 with the comparative example, A shows a comparative example, B shows an Example. The figure which shows the temporary increase in sludge level by the increase in raw water inflow. A graph showing a temporary increase in sludge level due to an increase in raw water inflow. The graph which shows an example of the excess sludge automatic extraction control by this invention. The figure which shows an example of the display screen of a sludge level meter. The figure which shows the whole flow of a waste water treatment system. The figure for demonstrating the conventional excess sludge extraction method in a final sedimentation basin.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the configuration of an automatic excess sludge extraction system according to the present invention, and parts corresponding to those in FIG.

  In this example, an ultrasonic sludge level meter 30 is used to measure the sludge level in the final sedimentation basin 13, and the extraction amount of surplus sludge is calculated from the sludge level output from the sludge level meter 30. The amount calculation means 41 is provided.

  The sludge level meter 30 includes an ultrasonic transducer 31 that transmits and receives ultrasonic waves and a main body 32. The main body 32 displays a transmission unit 33, a reception unit 34, a control unit 35, and a calculation unit 36 as shown in FIG. Part 37. The calculation unit 36 includes a sludge level calculation unit 36a, an averaging processing unit 36b, and a data processing unit 36c. The display unit 37 includes a liquid crystal display screen.

  Although the detailed illustration of the ultrasonic transducer 31 is omitted, it is attached to the final sedimentation basin 13 and emits ultrasonic waves perpendicularly to the bottom of the final sedimentation basin 13 and receives the reflected waves. Yes. The ultrasonic wave is emitted when the control unit 35 supplies a trigger pulse to the transmission unit 33 and the transmission pulse is supplied to the ultrasonic transducer 31 from the transmission unit 33 which has started the operation by the trigger pulse.

  The reflected wave is received by the receiver 34, and the received signal is input from the receiver 34 to the sludge level calculator 36a of the calculator 36.

  In this example, ultrasonic waves are emitted at a predetermined cycle, and the sludge level is constantly measured. To enable accurate and good measurement of the sludge level, the ultrasonic emission specifications are as follows. did.

・ Frequency: 200 kHz
-Pulse width: 0.00001 seconds-Number of pulse firings: 14.7 times / second Further, the directivity angle of the ultrasonic transducer 31 was set to 8 degrees.

  Next, each process of the sludge level calculation part 36a, the averaging process part 36b, and the data process part 36c is demonstrated.

  The received signal input from the receiving unit 34 to the sludge level calculating unit 36a includes reflected signals from the final sedimentation basin bottom, the interface between treated water and sludge, floating sludge, etc., and the sludge level calculating unit 36a uses ultrasonic waves. Data processing such as time from launch to reception and identification by reflected signal strength is performed. Then, the sludge level (distance from the surface of the treated water to the interface between the treated water and the sludge) is obtained from the time until reception of the reflected signal having the second highest reflected signal intensity by data processing. The reflected signal having the highest reflected signal intensity is a reflected signal from the bottom of the final sedimentation basin. Data processing (sludge level calculation) in the sludge level calculation unit 36a is updated every 0.075 seconds in this example.

  Since the data updated every 0.075 seconds contains a lot of errors, if it is output as it is as a sludge level, it becomes a very unstable value. Therefore, the averaging processing unit 36b performs an averaging process so that stable data is set to the sludge level. FIG. 3 exemplifies the flow of the averaging process. In this example, the number of data used for averaging (the number of data processes) is 256 points.

  As shown in FIG. 3, the data from data 1 to data 256 is averaged and the first sludge level is output. This output takes 19.2 seconds. Subsequently, the second sludge level output averages data from data 2 to data 257. Thereafter, 256 sludge levels are averaged and output every time data is updated. The averaged sludge level data is output to the display unit 37 and displayed on the display screen. In addition, sludge level data averaged is output to the data processing unit 36c every second. The output period of the sludge level data to the data processing unit 36c is 1 second in this example, but is not limited to 1 second. The sludge level size, the rotational speed of the scraper 13a, etc. It is set appropriately according to The number of data used for averaging is 256 points in the above example, but is not limited to this.

  FIG. 4A shows an example of sludge level data output from the averaging processor 36b to the data processor 36c. As shown in FIG. 1, a scraper 13 a that rotates at a constant speed is installed in the final sedimentation basin 13 for the purpose of flattening sludge. The arm portion of the scraper 13 a is an ultrasonic transducer 31. Since the data passes under a predetermined cycle, it can be seen that the data in FIG. 4A has a level fluctuation caused by measuring the arm portion.

  The data processing unit 36c performs processing for removing level fluctuations caused by the scraper 13a. FIG. 5 shows a processing flow in the data processing unit 36c, and the processing flow will be described below.

  The determination of the presence or absence of the scraper 13a is X (t) (where t is the time) input data of the latest sludge level input from the averaging processing unit 36b to the data processing unit 36c, and the processing in the data processing unit 36c. When the data (output data) immediately before the sludge level calculated 1 second before in this example is A (t-1), these X (t) and A (t-1) are used. Done.

  However, since A (t-1) does not exist when the data processing unit 36c performs processing for the first time, it is necessary to use A (t-1) as an alternative, so that the data processing unit 36c performs data processing. Immediately before starting, the input data X (t-1) of the immediately previous sludge level calculated one second before by the averaging processing unit 36b is used as the first reference value A (t-1) instead (step S1). .

  Here, if the input data X (t−1) being passed by the scraper 13a first becomes the reference value A (t−1), data processing is not normally performed in the subsequent processing. Therefore, it is necessary to set A (t-1) to X (t-1) when the scraping machine 13a has not passed, and in the initial reference value selection in this step S1, processing as shown in FIG. I do. Hereinafter, the processing flow shown in FIG. 6 will be described.

  Ten pieces of sludge level input data X input from the averaging processing unit 36b in a cycle of 1 second are stored in time series (step S11). Subsequently, one piece of input data is acquired from the averaging processing unit 36b. This input data is X (t-1) (step S12). The input data X (t-1) is compared with the input data X (t-11) 10 seconds ago, and it is determined whether or not the absolute value of the difference is smaller than 0.1 m (step S13). When it is smaller, the judgment counter set to 10 in advance is decremented by 1 (step S14). Then, it is determined whether or not the determination counter has become 0 (step S15). If not, X (t-1) is set to X (t-2) (step S16), and the process returns to step S12.

  On the other hand, if it is determined in step S13 that the absolute value of the difference between X (t-1) and X (t-11) is 0.1 m or more, it is determined whether or not the determination counter is 20 (step S17). If it is not 20, the determination counter is incremented by 1 (step S18), and the process proceeds to step S15. If the determination counter is 20, the process proceeds directly to step S15 without adding +1 to the determination counter.

  Then, the above-described processing is sequentially repeated until the value of the judgment counter becomes 0, and when the value of the judgment counter becomes 0, the input data X (t−1) at that time is first set as the reference value A (t−1). Select. The determination counter is used to determine that the scraper 13a has not passed when it reaches 0. The determination counter has an upper limit value of 20, and the processing flow shown in FIG. 6 is executed. Thus, X (t−1) at the time when the scraping machine 13a has not passed can be set to the first reference value A (t−1).

  When the selection of the reference value A (t−1) is completed, the process proceeds to step S2 in FIG. 5 to determine the presence or absence of the scraper 13a and perform data processing.

  The determination in step S2 is performed by comparing the latest input data X (t) with the immediately preceding output data A (t-1). If the absolute value of the difference is smaller than 0.1 m, there is no scratching machine. If it is 0.1 m or more, it is determined that there is a scraping machine. If there is a scraper, the latest input data X (t) is invalidated, the immediately preceding output data A (t-1) is set to A (t) (step S3), and the data is output again. FIG. 7A shows data processing when the scraper is present.

On the other hand, when there is no scraper, output data A (t)
A (t) = {X (t) -A (t-1)} / N + A (t-1) (1)
(Step S4) and output. Here, N is a constant (average weight), for example, 128. Data processing in the case of no scraper is shown in FIG. 7B. When there is no scraper, the level fluctuation X (t) -A (t-1) is divided by the average weight N, and the value is added to the previous output data A (t-1) to obtain the latest output data. Let A (t).

  Here, the reason why N is set and A (t) is obtained from equation (1) will be described with reference to FIGS. 8A and 8B. FIG. 8A shows data processing when N is not set, and FIG. 8B shows data processing when N is set.

It is assumed that a level fluctuation of 0.09 m occurs accidentally in the input data X twice at times t ₃ and t ₄ . When N is not set, as shown in FIG. 8A, the difference between the input data X and the immediately preceding output data A is less than 0.1 m, so it is determined that there is no scratching machine, and the output data A is an accidental level. The input data X in which fluctuation has occurred is followed.

Next, when the input data X with no accidental level fluctuations at time t ₅ is inputted, the difference between the output data A of the immediately preceding is 0.18 m, will determine that raking machine Yes, Figure Since the data processing shown in FIG. 7A is performed, the output data A continues to output data that follows accidental level fluctuations, whereby the correct output data A cannot be obtained.

In contrast, for data processing shown in FIG. 7B is a case of setting the N, output data A at time t ₃ is as shown in FIG 8B, it is possible to suppress the influence of accidental level fluctuations it can. At time t ₄ , the difference between the input data X and the immediately preceding (time t ₃ ) output data A is 0.1 m or more. Therefore, it is virtually determined that there is a scraper, and the data processing shown in FIG. 7A Thus, the immediately preceding output data A is continuously output. At times t ₅ and t ₆ , the output data A gradually converges to the input data X by the data processing shown in FIG. 7B.

  In this way, when an accidental level fluctuation that is unlikely to be an actual sludge level fluctuation occurs, correct output data A (t) cannot be obtained if N is not set, whereas N is set, If the output data A (t) is obtained by the equation (1), it is possible to reduce a risk when an accidental level fluctuation occurs. In addition, although the value of N is set to 128 in the example mentioned above, it is not limited to this.

  The output data A (t) is obtained as described above. As shown in FIG. 5, A (t) is set to A (t-1) (step S5), and the output data A (t) is obtained from step S2. The process of step S5 is repeatedly executed. By performing such processing in the data processing unit 36c, the sludge level data after the data processing becomes as shown in FIG. 4B, and the level fluctuation caused by the scraper 13a is removed.

  The sludge level (output data A (t)) obtained by the sludge level meter 30 is always output to the extraction amount calculation means 41. This output is performed, for example, every minute, and the extraction amount calculation means 41 calculates the extraction amount of excess sludge from the input sludge level. The calculated extraction amount is input to the control valve adjustment means 23 through the sequencer 25, and the adjustment valve adjustment means 23 adjusts the adjustment valve 24 based on the input extraction amount, thereby discharging excess sludge.

  As in the conventional example shown in FIG. 14, the surplus sludge discharge path is provided with a flow meter 26, and the flow rate measured by the flow meter 26 is input to the control valve adjusting means 23 and the sequencer 25. The sludge level obtained by the sludge level meter 30, the withdrawal amount calculated by the withdrawal amount calculation means 41 and the flow rate measured by the flow meter 26 are transmitted from the sequencer 25 to the central control room 22 in this example. It has become a thing.

  The adjustment of the extraction amount by the control valve adjusting means 23 is considered to be performed by the PI control in which the D operation is omitted in the PID control, because it is considered that the fluctuation of the sludge level does not occur due to the characteristics of the sludge. Here, as shown in FIGS. 9 and 10, if the PI control is made too sensitive to the sludge level due to the phenomenon of the final sedimentation basin in which the sludge level temporarily increases due to an increase in the raw water inflow, Excessive withdrawal may lead to instability of downstream equipment. In order to cope with this phenomenon, the PI control is as follows.

・ In order to prevent excessive extraction of sludge, the P value and I value were increased to reduce the control sensitivity.
・ In anticipation of a temporary increase in the sludge level, a non-control zone (see FIG. 9) was provided near the target value of the sludge level.

  By performing the processing and control as described above, the excess sludge automatic extraction system according to the present invention can realize an automatic extraction system of excess sludge that stabilizes the sludge level near the target value. FIG. 11 illustrates this situation.

  In addition, since the ultrasonic wave has a characteristic of reflecting more strongly at the interface having a large density difference, in the present invention using the ultrasonic wave for measuring the sludge level, not only the interface position of the sludge and the treated water but also the interface of the interface. It is possible to know the condition, the density of the sedimentation sludge, the condition in the final sedimentation tank such as the sedimentation tank bottom. FIG. 12 shows an example of the display screen of the display unit 37 of the sludge level meter 30. From this display screen, it can be seen that the sludge state can be determined.

  Although the final sedimentation basin has been described above as an example, the sedimentation basin to which the present invention is applied is not limited to the final sedimentation basin. For example, when a plurality of sedimentation basins are installed in parallel or in series, it can be applied independently for each individual sedimentation basin, or a plurality of sedimentation basins can be linked and applied.

  In the above example, the criterion for determining the presence or absence of the scraper is 0.1 m, and for example, the difference between the input data X (t) and the immediately preceding output data A (t−1) is 0.1 m or more. At the time, it is determined that there is a scraper, but the criterion is not limited to 0.1 m, and is set to an appropriate value according to the conditions of the individual sedimentation basin.

Claims (2)

A system for automatically removing excess sludge in a wastewater treatment system sedimentation basin that separates treated water and sludge,
A sludge level meter that emits ultrasonic waves in a predetermined direction toward the bottom of the settling basin and includes an ultrasonic transducer that receives the reflected waves, and obtains the sludge level of the settling basin from the received reflected waves;
An extraction amount calculating means for calculating an extraction amount of excess sludge from the sludge level output from the sludge level meter;
A control valve adjusting means for adjusting a control valve for extracting excess sludge provided in the settling basin based on the extraction amount ;
Before Symbol sludge level meter,
An averaging processing unit for sequentially averaging and outputting sludge level data calculated from the reflected wave,
A data processing unit that processes sludge level data input from the averaging processing unit and outputs the data to the extraction amount calculating means;
When the input data input from the averaging processing unit is X (t) (where t is time) and the output data output to the extraction amount calculating means is A (t), the data processing unit is ,
When the difference between the immediately preceding output data A (t−1) and the input data X (t) is greater than or equal to a predetermined value, the immediately preceding output data A (t−1) is output as A (t) ,
When the difference is less than a predetermined value,
A (t) = {X (t) -A (t-1)} / N + A (t-1) (where N is a constant)
A surplus sludge automatic extraction system, which calculates and outputs A (t) by In the excessive sludge automatic extraction system according to claim 1 ,
The excess sludge automatic extraction system, wherein the sludge level meter includes a display unit that displays data of a sludge level averaged by the averaging processing unit.