JP2007248102A - Water quality measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate oxygen utilization speed by always accurately obtaining the dissolved oxygen concentration of drainage in a biological treatment tank by eliminating error factor due to dirt in a measuring tank and dirt of a dissolved oxygen concentration sensor. <P>SOLUTION: Measured water is circulated for a certain time, then stored in a water quality measuring tank 17, and aerated by a blower 29, the dissolved oxygen concentration is increased, and the period when the measured value of the dissolved oxygen concentration sensor 28 decreases from the upper limit to the lower limit is measured, thereby calculating the oxygen utilization speed of the measured water. The water quality measuring tank 17 and dissolved oxygen concentration sensor 28 are cleaned periodically. Thus, the measuring accuracy is increased by eliminating the error factor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention stores the mixed water of waste water and sludge, which is the treated water discharged from factories and other facilities, in the biological treatment tank, measures the dissolved oxygen concentration of the mixed water in the biological treatment tank, and uses oxygen. The present invention relates to a water quality measuring device for calculating speed.

  Conventionally, as a wastewater treatment method that measures the quality of the mixed water of wastewater and sludge, which is the treated water of the biological treatment tank, and controls the water quality to the optimum condition based on the detected value, directly into the mixed water of the biological treatment tank, Dissolved oxygen concentration detector is located to detect dissolved oxygen concentration (DO, Dissolved Oxygen), and there are some which control the aeration ability of the aeration means of the biological treatment tank based on this detected value. As a result, the detection value of the dissolved oxygen concentration detector becomes unstable, and it is difficult to detect an accurate value.

  In addition, it is necessary to install a dissolved oxygen concentration detector in a relatively large biological treatment tank, and there are problems in workability including maintenance. Furthermore, there is a problem that foreign substances in the mixed water are likely to adhere to the dissolved oxygen concentration detector due to fluidization of a large amount of the mixed water by aeration, making it difficult to detect an accurate value. In order to solve the above-mentioned problems, there is one that detects a dissolved oxygen concentration by taking a part of mixed water from a biological treatment tank into a separate measuring tank.

As a typical example, an annular water flow is formed by continuously flowing waste water into an annular water channel defined by a concentric cylindrical outer peripheral wall and a lower concentric cylindrical inner peripheral wall and a bottom wall between both peripheral walls. There is one that measures the quality of waste water by dropping a water quality measurement probe in an annular water flow (see, for example, Patent Document 1).
JP 2002-340883 A

  However, the conventional one described in Patent Document 1 has a low detection performance in a low concentration region of the dissolved oxygen concentration detector in a state where the dissolved oxygen concentration of the biological treatment tank is low, and various disturbances are also detected. It is difficult to detect an accurate value due to the influence.

  Therefore, it is difficult to accurately calculate the oxygen utilization rate from the detected dissolved oxygen concentration.

  The present invention solves the above-mentioned conventional problems, and always accurately grasps the dissolved oxygen concentration of the mixed water of wastewater and sludge, which is the treated water of the biological treatment tank, and accurately calculates the oxygen utilization rate. An object of the present invention is to provide a water quality measuring device capable of performing the above.

  A water quality measuring tank for storing a certain amount of measured water, a dissolved oxygen concentration sensor for measuring the dissolved oxygen concentration of the measured water stored in the water quality measuring tank, and a measured for supplying the measured water to the water quality measuring tank A water inlet, a washing water inlet for supplying washing water for washing the water quality measuring tank, an upper outlet for discharging measured water or washing water stored in the water quality measuring tank from an upper part of the water quality measuring tank, A water quality measuring device having a bottom outlet for discharging water to be measured or washing water stored in the water quality measuring tank from the bottom of the water quality measuring tank, wherein the water to be measured is supplied to the water quality measuring tank Water supply means, wash water supply means for supplying the wash water to the water quality measurement tank, bottom water discharge means for discharging measured water or wash water stored in the water quality measurement tank from the bottom outlet, and A circulating flow is generated in the water quality measurement tank. A circulating flow generating means, and aeration means for aeration of the measured water or washing water in the water quality measuring tank, the measured water supply means, the bottom outlet opening / closing means, the circulating flow generating means, and the aeration means A cleaning process for cleaning the water quality measuring tank and the dissolved oxygen sensor by controlling the water quality, a standby process for filling the water quality measuring tank with cleaning water, and oxygen of water to be measured based on the measured value of the dissolved oxygen sensor The water quality measuring device is characterized by having a control device that performs a calculation process for calculating a use speed.

  According to the present invention, the error factor due to dirt in the water quality measuring tank and the dissolved oxygen concentration sensor is eliminated, and the dissolved oxygen concentration in the waste water of the biological treatment tank is always accurately grasped, thereby accurately calculating the oxygen utilization rate. It is possible to provide a water quality measuring apparatus that can

  A water quality measurement apparatus according to a first embodiment of the present invention includes a water quality measurement tank that stores a certain amount of measured water, and a dissolved oxygen concentration sensor that measures the dissolved oxygen concentration of the measured water stored in the water quality measurement tank. A measured water inlet for supplying measured water to the water quality measuring tank, a cleaning water inlet for supplying cleaning water for cleaning the water quality measuring tank, and measured water or cleaning water stored in the water quality measuring tank A water quality measuring device comprising an upper outlet for discharging water from the upper part of the water quality measuring tank, and a bottom outlet for discharging measured water or washing water stored in the water quality measuring tank from the bottom of the water quality measuring tank. Measured water supply means for supplying the measured water to the water quality measurement tank, wash water supply means for supplying the wash water to the water quality measurement tank, and measured water stored in the water quality measurement tank or washing Water is discharged from the bottom outlet Bottom discharge means, circulating flow generating means for generating a circulating flow in the water quality measuring tank, and aeration means for aeration of the measured water or washing water in the water quality measuring tank, the measured water supply means, A cleaning step of cleaning the water quality measuring tank and the dissolved oxygen sensor by controlling a bottom outlet opening / closing means, the circulating flow generating means, and the aeration means; a standby process of filling the water quality measuring tank with cleaning water; It is characterized by having a control device that performs a calculation process for calculating the oxygen utilization rate of the water to be measured based on the measured value of the dissolved oxygen sensor.

  According to the present embodiment, the dissolved oxygen concentration of the water to be treated in the biological treatment tank can always be accurately grasped, and thereby the oxygen utilization rate can be accurately computed.

  The second embodiment of the present invention is characterized in that, in the water quality measurement apparatus according to the first embodiment, the cleaning step includes a measured water discharge operation, a cleaning water supply operation, and a cleaning operation. .

  According to the present embodiment, the water quality measuring tank and the dissolved oxygen concentration sensor can be effectively cleaned.

  According to a third embodiment of the present invention, in the water quality measurement apparatus according to the second embodiment, the measured water discharge operation is such that the measured water in the water quality measurement tank is discharged from the bottom discharge port by the bottom discharge means. It is intended to be discharged.

  According to the present embodiment, the water to be measured can be discharged.

  According to a fourth embodiment of the present invention, in the water quality measurement apparatus according to the second embodiment, the washing water supply operation is performed by measuring the water quality with the washing water supply means until the water level in the water quality measurement tank reaches a set water level. It is to be supplied to the tank.

  According to the present embodiment, an appropriate amount of washing water can be supplied to the water quality measurement tank.

  According to a fifth embodiment of the present invention, in the water quality measurement apparatus according to the second embodiment, the washing operation is performed by circulating the washing water in the water quality measurement tank by the circulation flow generating means. .

  According to the present embodiment, the water quality measuring tank and the dissolved oxygen concentration sensor can be washed by the circulating flow.

  According to a sixth embodiment of the present invention, in the water quality measurement apparatus according to the second embodiment, the cleaning operation is performed by aeration of the cleaning water in the water quality measurement tank by the aeration means.

  According to the present embodiment, the water quality measuring tank and the dissolved oxygen concentration sensor can be cleaned by bubbles generated by aeration.

  According to a seventh embodiment of the present invention, in the water quality measurement apparatus according to the second embodiment, a sensor cleaning water inlet for supplying cleaning water for cleaning the dissolved oxygen concentration sensor to the water quality measurement tank, and a sensor cleaning water Sensor cleaning water supply means for supplying water to the water quality measuring tank, and in the cleaning step, the sensor cleaning water supply means supplies sensor cleaning water to clean the dissolved oxygen concentration sensor and the bottom outlet opening / closing means. The sensor cleaning operation for opening the sensor drain and discharging the sensor cleaning water is provided.

  According to the present embodiment, the dissolved oxygen concentration sensor can be cleaned by spraying the sensor cleaning water to the dissolved oxygen concentration sensor.

  The eighth embodiment of the present invention is characterized in that, in the water quality measurement apparatus according to the first embodiment, the standby step includes a cleaning water discharge operation, a cleaning water supply operation, and a standby operation.

  According to this embodiment, deterioration of the dissolved oxygen concentration sensor can be prevented.

  According to a ninth embodiment of the present invention, in the water quality measurement apparatus according to the eighth embodiment, the washing water discharge operation discharges the water to be measured in the water quality measurement tank from the bottom discharge port by the bottom discharge means. It is what you do.

  According to the present embodiment, the cleaning water can be discharged.

  According to a tenth embodiment of the present invention, in the water quality measurement apparatus according to the eighth embodiment, the washing water supply operation is performed by the washing water supply means until the water level of the water quality measurement tank reaches the set water level. It is to be supplied to the tank.

  According to the present embodiment, cleaning water can be supplied to the water quality measurement tank.

  According to an eleventh embodiment of the present invention, in the water quality measuring apparatus according to the eighth embodiment, the standby operation is such that the water quality measuring tank is maintained in a state filled with washing water for a set time.

  According to the present embodiment, the water quality measurement tank can be kept in a state filled with the washing water, and the dissolved oxygen concentration sensor can be kept on standby until the next measurement is performed.

  According to a twelfth embodiment of the present invention, in the water quality measurement apparatus according to the first embodiment, the calculation step includes a washing water discharge operation, a measured water supply operation, an aeration operation, and a calculation operation. It is.

  According to the present embodiment, the oxygen utilization rate of the water to be measured can be accurately calculated.

  According to a thirteenth embodiment of the present invention, in the water quality measurement apparatus according to the twelfth embodiment, the washing water discharge operation causes the bottom discharge means to discharge the cleaning water in the water quality measurement tank from the bottom discharge port. It is a thing.

  According to the present embodiment, the cleaning water can be discharged.

  According to a fourteenth embodiment of the present invention, in the water quality measurement apparatus according to the twelfth embodiment, the measured water supply operation supplies measured water to the water quality measuring tank by the measured time measured water supply means. A circulation flow is generated in the water quality measurement tank by the generation of the circulation flow.

  According to the present embodiment, the properties of the water to be measured can be kept uniform.

  According to a fifteenth embodiment of the present invention, in the water quality measurement apparatus according to the twelfth embodiment, the aeration operation generates a circulation flow in the water quality measurement tank by the circulation flow generation means and measures the water quality by the aeration means. The measured water stored in the tank is aerated.

  According to the present embodiment, the dissolved oxygen concentration of the water to be measured can be increased uniformly.

  In the sixteenth embodiment of the present invention, in the water quality measurement apparatus according to the fifteenth embodiment, the aeration operation is performed until the measured value of the dissolved oxygen concentration sensor becomes equal to or higher than the set value.

  According to the present embodiment, the measured value of the dissolved oxygen concentration sensor can be increased to a value at which the oxygen utilization rate can be accurately calculated.

  In the water quality measurement apparatus according to the twelfth embodiment, the seventeenth embodiment of the present invention calculates the oxygen utilization rate of the water to be measured from the upper limit value where the measured value of the dissolved oxygen concentration sensor is preset to the lower limit value. The time until it falls down is measured.

  According to the present embodiment, the oxygen utilization rate can be calculated easily and accurately.

  The eighteenth embodiment of the present invention is characterized in that, in the water quality measuring apparatus according to the first embodiment, the cleaning process, the standby process, and the calculation process are periodically repeated.

  According to the present embodiment, the measurement error due to the contamination of the dissolved oxygen sensor and the measurement error due to the disturbance of the water flow can be eliminated, and the oxygen utilization rate can be accurately and automatically measured.

  In the nineteenth embodiment of the present invention, in the water quality measuring apparatus according to the eighteenth embodiment, the cleaning step is performed every several cycles.

  According to the present embodiment, the cleaning of the dissolved oxygen sensor and the water quality measuring tank can be kept to the minimum necessary, and the power consumption and the washing water consumption in the water quality measuring device can be saved.

  In the twentieth embodiment of the present invention, in the water quality measuring apparatus according to the eighteenth embodiment, the sensor cleaning operation is performed every several cycles of the cleaning step every several cycles.

  According to the present embodiment, cleaning of the dissolved oxygen sensor can be kept to a minimum, and power consumption and cleaning water consumption in the water quality measuring device can be saved.

  The twenty-first embodiment of the present invention is characterized in that, in the water quality measuring apparatus according to the first embodiment, the circulating flow generating means generates a vertical circulating flow in the water quality measuring tank.

  According to the present embodiment, it is possible to prevent sedimentation of suspended solids contained in the water to be measured supplied to the water quality measurement tank.

  Hereinafter, the water quality measuring apparatus of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram in which a water quality measuring apparatus according to Embodiment 1 of the present invention is connected to a biological treatment means 1. In addition, the arrow in a figure shows the flow of waste_water | drain.

  First, the configuration of the biological treatment means 1 will be described. Wastewater which is treated water is caused to flow into the biological treatment tank 4 from the inflow pipe 2 via the flow rate adjusting valve 3 and stored in a certain amount. Air from the blower 5 is supplied to the mixed water of waste water and sludge, which is the water to be treated in the biological treatment tank 4, through the supply pipe 6, the air diffusion pipe 7, and the numerous ejection holes 8 provided in the air diffusion pipe 7. By this aeration, the dissolved oxygen concentration of the mixed water in the biological treatment tank 4 is increased to be aerobic and promote decomposition by microorganisms. The mixed water purified in the biological treatment tank 4 is supplied to the sedimentation tank 10 through the connection pipe 9, and the sludge is separated by sedimentation and discharged through the discharge pipe 11 and the on-off valve 12. It returns to the biological treatment tank 4 as activated sludge. The treated water from which the sludge has been removed is discharged from the discharge pipe 13 and discharged or reused.

  Next, the configuration of the water quality measuring device 14 will be described. A pump 15, which is a measurement water supply means installed in the biological treatment tank 4, causes the measured water in the biological treatment tank 4 to flow into the water quality measurement tank 17 through the measured water inflow pipe 16. The measured water inflow pipe 16 is provided with a flow meter 18 for measuring the flow rate of the measured water flowing in and a measured water introduction valve 19 for adjusting the flow rate of the flowing measured water.

  An upper outlet 20 is provided at the top of the water quality measuring tank 17, and a bottom outlet 21 is provided at the bottom of the water quality measuring tank 17. Tap water and water to be measured, which will be described later, are supplied from the upper outlet 20. By overflowing, it can return to the biological treatment tank 4 through the discharge pipe 22. Further, by opening the discharge valve 23 which is a bottom discharge means, it is possible to recirculate from the bottom discharge port 21 through the discharge pipe 22 to the biological treatment tank 4.

  In addition, a cleaning water inflow pipe 24 that supplies tap water as cleaning water and a cleaning water introduction valve 25 that opens and closes the supply of tap water are provided in the upper part of the water quality measurement tank 17, and the cleaning water introduction valve 25 is opened. Then, the cleaning water is supplied to the water quality measuring tank 17.

  The bottom of the water quality measurement tank 17 is provided with a sensor cleaning water inflow pipe 26 for supplying tap water as sensor cleaning water and a sensor cleaning valve 27 for opening and closing the supply of tap water. The sensor cleaning water can be sprayed to the dissolved oxygen concentration sensor 28 that detects the dissolved oxygen concentration provided in the water quality measurement tank 17 to clean the dissolved oxygen concentration sensor 28.

  Further, the water quality measurement tank 17 is provided with a supply pipe 30 connected to a blower 29 as an aeration means, and an air diffuser pipe 31 connected to the supply pipe 30 and having a large number of jet nozzles. This is performed by supplying air from the blower 29 to the supply pipe 30 and the diffuser pipe 31 to the water to be measured in the measurement tank 17. By this aeration, the dissolved oxygen concentration of the water to be measured in the water quality measurement tank 17 is made higher than the dissolved oxygen concentration of the water to be treated in the biological treatment tank 4.

  Further, an underwater mixer 32 is installed in the water quality measuring tank 17 as a circulating flow generating means for generating a vertical circulating flow.

  Further, a water level sensor 33 that measures the water level of the water to be measured that has flowed into the water quality measurement tank 17 is provided in the water quality measurement tank 17.

  FIG. 2 is a block diagram showing input / output of the control device 34. The control device 34 receives the measured value of the flow meter 18, the measured value of the dissolved oxygen concentration sensor 28, and the measured value of the water level sensor 33 as inputs, and operates / stops the command to the pump 15 and the opening command to the measured water introduction valve 19. , Open / close command to the discharge valve 23, open / close command to the cleaning water introduction valve 25, open / close command to the sensor cleaning valve 27, operation / stop command to the blower 29, operation to the underwater mixer 32 / Output a stop command.

  Next, the operation of the control device 34 will be described.

  FIG. 3 is a block diagram showing the transition of the control operation of the control device 34, and FIG. 4 is a diagram showing the operation of each device in each control operation of the control device 34.

  When the water quality measuring device 14 is turned on, the control device 34 first opens the discharge valve 23 as the measured water discharge operation (S1) in the cleaning process, and the measured water in the water quality measuring tank 17 is discharged from the bottom outlet 21. Reflux to the biological treatment tank 4.

  After 1 minute, the flow shifts to the sensor cleaning operation (S2), the discharge valve 23 and the sensor cleaning valve 27 are opened, the cleaning water is injected to the dissolved oxygen concentration sensor 28, the dissolved oxygen concentration sensor 28 is cleaned, and the cleaning water is discharged to the bottom. Reflux from the outlet 21 to the biological treatment tank 4.

  After a lapse of one minute, the operation proceeds to the washing water supply operation (S3), the discharge valve 23 and the sensor washing valve 27 are closed, and the washing water introduction valve 25 is opened to supply the washing water to the water quality measuring tank 17.

  The amount of cleaning water supplied to the water quality measuring tank 17 is measured by the water level sensor 33. When a predetermined amount is supplied, the operation proceeds to the cleaning operation (S4), and the water quality measurement is performed with the cleaning water introduction valve 25 open. While supplying the wash water to the tank 17, the blower 29 and the underwater mixer 32 are operated to wash the water quality measurement tank. The washing water overflows from the upper discharge port 20 and is returned to the biological treatment tank 4.

  After one minute has elapsed, the washing process is terminated, the process proceeds to the washing water discharge operation (S5) of the standby process, the blower 29 and the underwater mixer 32 are stopped, the washing water introduction valve 25 is closed, the discharge valve 23 is opened, and the water quality measuring tank 17 The washing water inside is refluxed from the bottom discharge port 21 to the biological treatment tank 4.

  After one minute has passed, the operation proceeds to the washing water supply operation (S6), the discharge valve 23 is closed, and the washing water introduction valve 25 is opened to supply washing water to the water quality measuring tank 17.

  When the amount of washing water supplied to the water quality measuring tank 17 is measured by the water level sensor 33 and a predetermined amount is supplied, the washing water introduction valve 25 is closed and the operation proceeds to the standby operation (S7).

  The standby operation is continued until 60 minutes have elapsed since the start of the operation of supplying the measured water in the calculation process (this means that the oxygen utilization rate is calculated at 60-minute intervals).

  Thereafter, the standby process is terminated, the process proceeds to the washing water discharge operation (S8) of the calculation process, the discharge valve 23 is opened, and the cleaning water in the water quality measurement tank 17 is refluxed from the bottom discharge port 21 to the biological treatment tank 4.

  After 1 minute has passed, the operation proceeds to the measured water supply operation (S9), the discharge valve 23 is closed, the pump 15 is operated, and the treated water in the biological treatment tank 4 is caused to flow into the water quality measuring tank 17 as measured water. The inflow flow rate of the water to be measured is measured by the flow meter 18, and the opening degree of the water to be measured introduction valve 19 is controlled so as to be a predetermined inflow rate. The measured water supply operation is such that the measured water overflows from the upper outlet 20 and returns to the biological treatment tank 4 so that the properties of the measured water in the water quality measurement tank 17 and the wastewater of the biological treatment tank 4 become equal. Is performed for a certain time (10 minutes).

  In the operation of supplying water to be measured, the underwater mixer 32 is also operated to generate a circulating flow in the vertical direction to prevent sedimentation of floating substances contained in the water to be measured.

  Thereafter, the operation proceeds to the aeration operation (S10), the pump 15 is stopped, the measured water introduction valve 19 is closed, and the underwater mixer 32 and the blower 29 are operated to dissolve the measured water stored in the water quality measuring tank 17. Increase oxygen concentration. The aeration operation is performed until the dissolved oxygen concentration of the water to be measured stored in the water quality measuring tank 17 is sufficiently higher than the wastewater dissolved oxygen concentration of the biological treatment tank 4 (8.0 mg / L).

  Next, a transition is made to the calculation operation (S11), the underwater mixer 32 continues to operate, and the blower 29 stops.

  In the calculation operation, the measured value of the dissolved oxygen concentration sensor 28 is monitored, the time T when the measured value of the dissolved oxygen concentration sensor 28 decreases from 8.0 mg / L to 3.0 mg / L is measured, and the oxygen utilization rate Rr is set to Rr. = 5 / T.

  After completing the calculation of the oxygen utilization rate Rr, the calculation process is terminated, the process proceeds to the discharge operation (S1) of the cleaning process, and the same operation is periodically repeated.

  The cleaning process (measured water discharge operation (S1) → sensor cleaning operation (S2) → washing water supply operation (S3) → cleaning operation (S4)) is performed every several cycles, and the water quality measuring tank 17 is more than necessary. In addition, the dissolved oxygen concentration sensor 28 is washed so that tap water is not wasted.

  In addition, since the sensor dirt is also removed to some extent by the circulating flow during the cleaning operation (S4), the normal cleaning process is performed without the sensor cleaning operation (S2), and the sensor cleaning operation (S2) is performed once every several cleaning processes. You may go.

  In the first embodiment, the underwater mixer 32 is used as the circulating flow generating means. However, a guide plate may be used in the center of the water quality measuring tank 17.

  Further, the supply amount of the cleaning water is measured by the water level sensor 33. However, if the supply flow rate and the retained water amount up to the overflow water level are known, the water level sensor 33 is not used and the supply can be performed at the set time.

  In addition, the time described in the first embodiment is a standard time unless specifically described, and is not limited to the described time.

  As described above, according to the wastewater treatment method of the present invention, the water to be measured is circulated in the water quality measurement tank 17, the water to be measured is aerated by the blower 29, and the dissolved oxygen concentration is increased from that of the biological treatment tank 4. Periodic cleaning of the water quality measurement tank 17 and the dissolved oxygen concentration sensor 28, and filling the water quality measurement tank 17 with cleaning water and waiting for it to perform biological treatment with the minimum required power consumption and cleaning water usage It is possible to provide a water quality measuring device capable of accurately grasping the oxygen utilization rate of the mixed water in the tank 4 at regular time intervals.

  The water quality measuring apparatus according to the present invention can be applied to various wastewater discharged from factories, wastewater treatment facilities, and the like.

The block diagram which shows the water quality measuring apparatus of Embodiment 1 by this invention Block diagram showing input / output of control device Block diagram showing control operation transition of control device The figure which shows operation | movement of each apparatus in each control operation | movement of a control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biological treatment means 2 Inflow pipe 3 Flow control valve 4 Biological treatment tank (drainage storage tank)
DESCRIPTION OF SYMBOLS 5 Blower 6 Supply pipe 7 Air diffuser 8 Ejection hole 9 Connection pipe 10 Precipitation tank 11,13,22 Discharge pipe 12 On-off valve 14 Water quality measuring device 15 Pump 16 Water to be measured 17 Water quality measurement tank 18 Flow meter 19 Water to be measured introduction Valve 20 Upper outlet 21 Bottom outlet 23 Drain valve 24 Wash water inflow pipe 25 Wash water introduction valve 26 Sensor wash water inflow pipe 27 Sensor wash valve 28 Dissolved oxygen concentration sensor 29 Blower 30 Supply pipe 31 Aeration pipe 32 Underwater mixer 33 Water level sensor 34 Control device

Claims (21)

A water quality measuring tank for storing a certain amount of water to be measured;
A dissolved oxygen concentration sensor for measuring the dissolved oxygen concentration of the water to be measured stored in the water quality measurement tank;
A measured water inlet for supplying measured water to the water quality measuring tank;
A washing water inlet for supplying washing water for washing the water quality measurement tank;
An upper outlet for discharging measured water or washing water stored in the water quality measurement tank from the upper part of the water quality measurement tank;
A water quality measuring device having a bottom outlet for discharging water to be measured or washing water stored in the water quality measuring tank from the bottom of the water quality measuring tank,
Measured water supply means for supplying the measured water to the water quality measurement tank;
Cleaning water supply means for supplying the cleaning water to the water quality measurement tank;
Bottom discharge means for discharging measured water or wash water stored in the water quality measurement tank from the bottom discharge port;
A circulating flow generating means for generating a circulating flow in the water quality measuring tank;
Aeration means for aeration of the water to be measured or the washing water in the water quality measurement tank,
By controlling the measured water supply means, the bottom discharge means, the circulating flow generation means, the aeration means,
A cleaning step of cleaning the water quality measuring tank and the dissolved oxygen sensor;
A standby step of filling the water quality measuring tank with washing water;
A water quality measuring apparatus comprising a control device for performing a calculation process for calculating an oxygen utilization rate of water to be measured based on a measured value of the dissolved oxygen sensor. The water quality measuring device according to claim 1, wherein the cleaning step includes a measured water discharge operation, a cleaning water supply operation, and a cleaning operation. 3. The water quality measuring apparatus according to claim 2, wherein the measured water discharge operation discharges the measured water in the water quality measuring tank from the bottom discharge port by the bottom discharge means. 3. The water quality measuring apparatus according to claim 2, wherein the cleaning water supply operation supplies the cleaning water to the water quality measuring tank by the cleaning water supply means until the water level of the water quality measuring tank reaches a set water level. The water quality measuring device according to claim 2, wherein the washing operation is performed by circulating the washing water in the water quality measuring tank by the circulating flow generating means. The water quality measuring apparatus according to claim 2, wherein the cleaning operation is performed by aeration of the cleaning water in the water quality measuring tank by the aeration means. A sensor cleaning water inlet for supplying cleaning water for cleaning the dissolved oxygen concentration sensor to the water quality measuring tank, and a sensor cleaning water supply means for supplying sensor cleaning water to the water quality measuring tank,
The cleaning step has a sensor cleaning operation in which sensor cleaning water is supplied by the sensor cleaning water supply means, the dissolved oxygen concentration sensor is cleaned, and the bottom outlet opening / closing means is opened to discharge the sensor cleaning water. The water quality measuring device according to claim 2. The water quality measuring device according to claim 1, wherein the standby step includes a cleaning water discharge operation, a cleaning water supply operation, and a standby operation. 9. The water quality measuring apparatus according to claim 8, wherein the washing water discharging operation discharges the water to be measured in the water quality measuring tank from the bottom discharge port by the bottom discharging means. 9. The water quality measuring apparatus according to claim 8, wherein the washing water supply operation supplies the washing water to the water quality measuring tank by the washing water supply means until the water level of the water quality measuring tank reaches a set water level. The water quality measuring device according to claim 8, wherein the standby operation maintains the water quality measuring tank for a set time in a state where the washing water is filled. The water quality measuring device according to claim 1, wherein the calculation step includes a washing water discharge operation, a measured water supply operation, an aeration operation, and a calculation operation. 13. The water quality measuring apparatus according to claim 12, wherein the washing water discharging operation discharges the water to be measured in the water quality measuring tank from the bottom discharge port by the bottom discharging means. The measured water supply operation is characterized in that the measured water is supplied to the water quality measurement tank by the measured water supply means for a set time and a circulating flow is generated in the water quality measurement tank by the circulating flow generating means. The water quality measuring device described. The aeration operation generates a circulating flow in the water quality measurement tank by the circulating flow generation means and aerates the water to be measured stored in the water quality measurement tank by the aeration means. Water quality measuring device. 16. The water quality measuring apparatus according to claim 15, wherein the aeration operation is performed until a measured value of the dissolved oxygen concentration sensor becomes a set value or more. The calculation operation is to calculate an oxygen utilization rate of water to be measured by measuring a time until the measured value of the dissolved oxygen concentration sensor falls from a preset upper limit value to a lower limit value. 12. The water quality measuring apparatus according to 12. The water quality measuring device according to claim 1 or 7, wherein the washing step, the standby step, and the calculation step are periodically repeated. The water quality measuring device according to claim 18, wherein the washing step is performed every several cycles. 19. The water quality measuring apparatus according to claim 18, wherein the sensor cleaning operation is performed every several cycles of the cleaning process. The water quality measuring device according to claim 1, wherein the circulating flow generating means generates a vertical circulating flow in the water quality measuring tank.

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