JPS59212755A - Device for measuring oxygen utilizing speed - Google Patents

Abstract

PURPOSE:To enable exact calculation of an oxygen utilizing speed by providing a calculator for a correction value which calculates the correction value from the ratio between the signal from an oxygen measuring device and the preliminarily stored partial pressure of oxygen in air and an arithmetic processor. CONSTITUTION:Air is filled in a measuring device 21 and the partial pressure P of the oxygen in the air measured with an oxygen measuring device 33 by the signal from a dissolved oxygen electrode 3 exposed in the air is inputted to a calculator 35 for a correction value. The calculator 35 calculates a correction value G from the preliminarily stored partial pressure P0 of the oxygen in the air by the value G= the pressure P0/the measured value P and inputs the same to an arithmetic processor 36. The equation I is corrected by using the value G as shown by the equation II and the exact oxygen utilizing speed can be calculated in the processor 36. In the equations, C0 is the prescribed concn. of the dissolved oxygen attained by aeration, T is the measuring time after the stop of aeration and CT is the concn. of the dissolved oxygen in the sample water after the time T.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an oxygen utilization rate measuring device for measuring the oxygen utilization rate of a mixed liquid in an aeration tank in activated sludge treatment.

[Technical background of Rara Ming and its problems] What is the activated sludge treatment method? Microorganisms present in the activated sludge in the aeration tank oxidize organic pollutants contained in sewage using oxygen dissolved in the water. It consists of doing.

Therefore, since C1 microorganisms consume dissolved oxygen in water, it is necessary to constantly supply oxygen through aeration. This is combined with the amount of oxygen required by the microorganisms themselves to sustain life.For the above reasons, the rate of oxygen utilization by microorganisms is an important indicator for activated sludge treatment.

A conventional oxygen utilization rate measuring device has the structure shown in FIG.
A dissolved oxygen electrode 3 is attached so as to be in contact with the sample water. Furthermore, on-off valves 4.5 made of pinch pulp or the like are provided at the upper and lower parts of the measuring container 2, respectively. Inside the measurement container 2, a rotor 6 for stirring the sample water and an aeration air supply port 8 for aeration are provided. A rotor 6 is installed on the outer wall of the measurement container 2.
Attach the star rough that drives the. The on-off valves 4 and 5 and the aeration air supply port 8 are air supply valves such as solenoid valves 9°to, t.
Air supply device 1 such as a compressor or instrument air via t
Connected to 2. The output of the dissolved oxygen' electrode 3 is sent to the dissolved oxygen measuring device 13 and measured as the dissolved oxygen concentration. Air supply valves 9.10.11 and stirruffs are wired to process controller 15.

The arithmetic processor 14 includes the dissolved oxygen measuring device 4 and the process controller 1.
Wired to 5.

In the above configuration, the air supply valve 9 is controlled by the process controller 15.
．． [O is controlled to open the on-off valves 4 and 5, and the rotor 6 is driven by the stirruff to replace the sample water in the measurement container 2 with the surrounding sample water. Next, the on-off valve 5 is closed, and air is supplied through the aeration air supply port 8 for aeration. At this time, the dissolved oxygen concentration in the sample water is measured by the dissolved oxygen electrode 3 and the dissolved oxygen measuring device 13, and when the arithmetic processor 14 determines that the dissolved oxygen concentration has reached a certain value, the process controller 15 to stop. Next, after stopping the stirruff, the on-off valve 4 is closed in a bubble-free state, and the sample water is sealed in the measurement container 2. After this, re-drive Starruff. In this way, the decrease in dissolved oxygen concentration is measured while the sample water is stirred by the stirruff, and the oxygen utilization rate is calculated by the arithmetic processor 14 according to the following equation (1).

C(l CT Oxygen utilization rate [l is also r (IIIP/e・hour)] = □・・
・(1) where, co is the predetermined dissolved oxygen am reached by aeration, T is the measurement time after stopping the aeration, C,
is the dissolved oxygen concentration of the sample water after 1 hour.

However, in the conventional oxygen utilization rate measuring device, as the measurement continues, dirt in the sample water adheres and accumulates on the inner wall of the measurement container 2 and the surface of the dissolved oxygen electrode 3. The dirt that adheres to and accumulates on the surface of the dissolved oxygen electrode 3 changes the characteristics of the dissolved acid violet and causes measurement errors. Adhesion and accumulation of dirt on the inner wall of the measuring container 2 may make it difficult to introduce sample water into the measuring container 2 and discharge the sample water from the measuring container 2, or cause the on-off valves 4 and 5 to malfunction, causing the measuring container to close. The sample water cannot be sealed inside the chamber, resulting in measurement errors.

Further, the dissolved oxygen electrode 3 causes fluctuations in measured values not only due to measurement errors due to adhesion and accumulation of dirt, but also due to deterioration of the internal liquid and the detection electrode over time.

Therefore, in the conventional oxygen utilization rate measuring device, the measured value of the dissolved oxygen electrode 3 is periodically inspected, and if the inspector deems it necessary based on the state of dirt adhesion and accumulation, the inner wall of the measurement container 2 is inspected. The surface of the dissolved oxygen electrode 3 was being cleaned. However, in order to carry out inspection and cleaning, it is necessary to take the measurement container 2 out of the aeration tank 1 and remove the dissolved oxygen electrode 3 and the on-off valves 4 and 5. After inspection and cleaning, it is naturally necessary to reinstall the measurement container 2 into the aeration tank 1, and these operations are troublesome and take a long time. Additionally, inspection requires equipment to produce a saturated dissolved oxygen solution.

[Object of the Invention] An object of the present invention is to ensure that sample water to be measured is introduced into a measurement container, and to be reliably discharged after the measurement, while the measurement container and dissolved oxygen electrode are immersed in an aeration tank. An object of the present invention is to provide an oxygen utilization rate measuring device that can perform cleaning of the inside of a measurement container and the surface of a dissolved oxygen electrode, and inspection and calibration of the dissolved oxygen electrode, and can obtain an accurate oxygen utilization rate measurement value.

[Summary of the Invention] The oxygen utilization rate measuring device according to the present invention comprises a measuring container immersed in a solution and having an air supply port for aeration and cleaning at the bottom, and on-off valves attached to the upper and lower parts of the measuring container. ,
A dissolved oxygen electrode is placed in contact with the sample water in the measurement container, an oxygen measuring device measures the dissolved oxygen in the solution or the oxygen partial pressure in the gas from the signal from this dissolved oxygen electrode, and the upper opening/closing valve is closed. A process controller that controls the process of opening an on-off valve and supplying air into the measurement container, and a signal from an oxygen measuring device with air being supplied into the measurement container and known atmospheric oxygen stored in advance. It is equipped with a correction value calculator that calculates a correction value from the ratio with the partial pressure, and a processor that calculates the oxygen utilization rate while correcting it based on the signal from the correction value calculator.

[Embodiments of the invention]

The present invention will be explained below with reference to an embodiment shown in the drawings. In FIG. 2, an aeration air supply port 22 and a cleaning air supply port 23 are provided in the F section of the measurement container 21. The cleaning air supply port 23 is connected to an air supply device 26 via an air supply valve 24 such as a solenoid valve and a flow rate regulator 25 such as a flow rate control valve or a capillary. The aeration air supply port 22 is also connected to the air supply device 26 via an air supply valve 27 and a flow rate regulator 28 . The air supply device 26 includes an air supply valve 29.30 and a flow rate regulator 31.
,．． It is also connected to the on-off valve 4.5 via 32. The oxygen measuring device 33 is wired to the dissolved oxygen electrode 3, the process controller 34, the correction value calculator 35, and the arithmetic processor 36. The correction value calculator 35 is wired not only to the oxygen measuring device 33 but also to the arithmetic processor 36 and the process controller 34, and is also wired between the arithmetic processor 36 and the process controller 34.

Next, the effect will be explained. The operation consists of the following seven steps, all of which are controlled by the process controller 34. In the first step, the on-off valve 4 at the top of the measurement container 2'' is closed, the on-off valve 5 at the bottom is opened, and the air supply device 26 supplies air, which has been adjusted to an appropriate flow rate with the flow regulator 25, through the air supply valve 24. From the cleaning air supply port 23 to the measuring container 21
The sample water in the measurement container 2 is discharged from the on-off valve 5 into the aeration tank and filled with air. In the second step, the measurement container 2
1, the air in the measuring container 21 is discharged from the opening/closing valve 4, and the air in the measuring container 21 is discharged from the aeration tank 1.
Introduce sample water into the chamber. In the third step, the on-off valve 4 at the top of the measurement container 21 is opened, the on-off valve 5 at the bottom is closed, and the air, which has been adjusted to an appropriate flow rate by the flow rate regulator 28, is supplied to the air supply valve 27.
The air is supplied from the aeration air supply port 22 through the measurement container 2.
Aerate the solution in 1. In the fourth step, the upper and lower on-off valves 4 and 5 are closed, and the star rough is operated to rotate the rotor 6. In the fifth step, the upper opening/closing valve 4 is opened and the lower opening/closing valve 5 is closed to supply air into the measurement container 21 through the cleaning air supply port 23 . In the sixth step, the on-off valve 4 is closed,
Open the on-off valve 5 and remove the measurement container 2 from the aeration air supply port 22.
Supply air into 1. In the seventh step, the on-off valve 4.5 is opened and the stirruff is operated.

The above seven steps are controlled by the process controller 34 as follows to perform water sampling, measurement, and cleaning five calibrations.

This is repeated as one standby cycle. Water sampling is performed through a first step and a second step. That is, in the first step, the sample water is completely discharged by filling the measuring container 21 with air, and in the next second step, the air inside the measuring container 2 is naturally discharged from the opening/closing valve 4 at the top. , sample water is introduced into the measurement container 21 through the on-off valves 4 and 5, and water is sampled. In order to more reliably replace the sample water, repeat the water sampling in the first step and second step several times. After the water sampling is completed, the third and fourth steps are carried out in sequence. That is, in the third step, the sample water sampled in the measurement container 21 is aerated with air supplied from the aeration air supply port 22. The third step ends when the dissolved oxygen concentration in the sample water measured by the dissolved oxygen electrode 3 and the oxygen measuring device 33 reaches a predetermined value. In the next fourth step, the sample water in the measurement container 21 is allowed to stand still, the air bubbles inside are floated and discharged, and then sealed, the dissolved oxygen concentration is measured while being stirred by the rotor 6, and the oxygen Calculate usage speed.

Cleaning is carried out by performing a first step, a second step, and a fifth step in this order after the measurement is completed. That is, after the measurement is completed, the sample water remaining in the measurement container 21 is discharged with cleaning air in the first step. At this time, since the cleaning air supply port 34 is provided at the bottom of the measurement container 21, the interface between the sample water and the air always descends in an undulating state inside the measurement container 21, so that the dissolved oxygen is connected to the surface of the electrode 3 and the inner wall of the measurement container 21. The dirt deposited on the inner wall of the on-off valve 5 is removed. At the same time, it is also cleaned by the movement and destruction of air bubbles in the sample water.

In the first step, the amount of air for cleaning must be larger than the amount of air for aeration because discharging the sample water from the measurement container 21 in a short time brings about a great cleaning effect. That is, while the amount of air for aeration is sufficient for 0.3 to 3 e/min,
The amount of air for cleaning is required to be 5 to 20 e/min. In the next second step, sample water is introduced into the measurement container 21, and then in the fifth step
In the process, cleaning air is supplied into the sample water and the on-off valve 4 at the top
Now clean the air bubbles for 4T. In order to perform the above cleaning more reliably, it is recommended to repeat it several times.

Calibration is performed in the sixth step. That is, after cleaning is completed, the sample water remaining in the measurement container 21 is discharged with aeration air in the sixth step, and the oxygen content in the air in the measurement container 21 is removed with the dissolved oxygen electrode 3 exposed to the air. The pressure is measured by an oxygen measuring device 33 based on a signal from the dissolved oxygen electrode 3. At this time, the oxygen measuring device 33 is switched to the oxygen partial pressure in the gas rather than the dissolved oxygen concentration based on a signal from the process controller 34. The partial pressure of oxygen in the atmosphere can be easily calculated from atmospheric pressure and humidity. In the case of the oxygen utilization rate measuring device of the present invention, the air pressure and humidity within the measurement container 21 change little, and the oxygen partial pressure may be kept approximately constant.

However, if sample water adheres to the surface of the dissolved oxygen electrode 3, the measured value will not be stable, but will stabilize as the surface of the dissolved oxygen electrode 3 dries. The time required for this stabilization is about 1 to 5 minutes.

The relationship shown in FIG. 3 is shown in FIG. 3 between the change over time of the measured value of the partial pressure of acidity in the air (hereinafter referred to as the air measurement value) in the measurement container 2 and the change over time of the oxygen utilization rate. I made sure that there was. The horizontal axis in FIG. 3 is the measurement period, and the vertical axis is the instruction fluctuation over time. The solid line a shows the indicated variation in air measurements, and the dashed line a shows the indicated variation in the oxygen utilization rate. From the solid line a, the air measurement value hardly changes for a while from the start of the measurement, or after that, the indication gradually decreases due to the adhesion of dirt to the surface of the dissolved oxygen electrode 3. Although it depends on the properties of the sample water, the indication often begins to drop within 1 to 2 months, and then drops by 50 inches or more over the next 1 to 2 months. As shown in FIG. 3, the fluctuation in the measured air value and the indicated fluctuation in the oxygen utilization rate indicated by the broken line almost coincide with #1. The oxygen utilization rate is calculated from the dissolved oxygen concentration in test #1 water, so it does not completely match the fluctuation of the air measurement value, but the required accuracy of the oxygen utilization rate is about ±5 inches, and the fluctuation of the air measurement value is used. It was confirmed that sufficient practical pressure compensation could be achieved.

After considering the above-mentioned readability, we were able to perform the calibration as shown below. That is, the measurement container 21 is filled with air in the sixth step, and the partial pressure of oxygen in the air measured by the oxygen measuring device 33 is adjusted to a corrected value based on the signals from the air 1 + the exposed bath oxygen electric and 3 gases. Input to the extractor 36. The correction value calculator 36 calculates a correction value G from the pre-stored oxygen partial pressure Cpo> in the air using equation (2), and inputs it to the deductive processor 35. The arithmetic processor 35 corrects equation (1) using correction value G, as shown in equation (3), and can calculate an accurate oxygen utilization rate.

Standby is carried out by performing the seventh step after the calibration is completed, and is a state in which the sample water is flowing in the measurement container 21 by the rotational force of the rotor 6, and the aeration time and dissolved oxygen concentration during measurement are reduced. Since time is not constant, this adjustment time is used to keep the time required for one cycle constant.

In the above example, one cycle consisted of water sampling, measurement, cleaning, two calibrations, and standby, but since water sampling consists of the JJI process and the second process, which corresponds to a part of cleaning, cleaning and water sampling were combined. Water sampling and measurement 9 calibrations.

Waiting can take l cycles. In this case, cleaning water sampling is performed in the 1st step, 2nd step, 5th step, [step, 2nd step]
If it is a process, the same effect as the above embodiment can be obtained.

Further, it is not necessary to carry out the calibration after measurement, and the same effect as the embodiment shown in FIG. 2 can be obtained no matter where the calibration is carried out. moreover,
Calibration can be carried out not only in the 6th step, but also by filling the measurement content 21 with all air, and can also be carried out in the 6th step. Therefore, in combination with water sampling or cleaning, 11 calibrations Water sampling and cleaning calibration.

It can be either a cleaning calibration water sampling. Squeezing water sampling and washing calibration may be carried out in the same process as water sampling and washing in the embodiment shown in FIG. Calibration can also be performed during the process.

The standby state is not limited to the seventh step, and may be a state in which air is started to be supplied into the measurement container 21. Alternatively, it may be omitted if necessary without affecting the effects of the present invention.

FIG. 4 shows another embodiment of the present invention, in which on-off valves 4,
5 are connected to strainers 41 and 42, respectively, and an aeration and cleaning air supply port 43 that has a common aeration air supply port and a cleaning air supply port is provided at the bottom of the measurement container 44. Strainers 41 and 42 contain hair that mixes into the sample water.
This prevents large debris such as vinyl and wood chips from flowing into the measuring container 21 and interfering with the rotation of the rotor 6. The stains on the strainers 41 and 42 can be removed simultaneously and effectively by cleaning the inner wall of the measurement container 44, the surface of the dissolved oxygen electrode 3, and the on-off valves 4 and 5 by carrying out the same cleaning as in the embodiment shown in FIG. Washed properly. Air supply port 4 for aeration and cleaning
The aeration air and cleaning air supplied into the measurement container 44 from the flow controllers 25 and 28 are adjusted to appropriate flow rates, respectively, and the process controller 34 controls the air supply valves 24 and 34 to adjust the flow rates to appropriate levels. By controlling and selectively supplying j7, the same effects as the embodiment shown in FIG. 2 can be obtained, and the measuring instruments and piping that are useful for preventing contamination can be simplified. It goes without saying that this can also be applied to the embodiment shown in FIG.

〔Effect of the invention〕

As explained above, according to the oxygen utilization rate measuring device of the present invention, there is a means for reliably introducing sample water into the measurement container;
In addition to having a means to ensure discharge, is there a measuring device? :J
With the dissolved oxygen electrode and the dissolved oxygen electrode immersed in the aeration tank, remove the dirt that accumulates on the inner wall of the measuring container, the on-off valve, and the surface of the dissolved oxygen tube, and perform the inspection and calibration of the dissolved oxygen electrode. This makes it possible to always accurately measure the oxygen utilization rate.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing the configuration of a conventional oxygen utilization rate measuring device, Fig. 2 is a system diagram showing an embodiment of the oxygen utilization rate measuring device of the present invention, and Fig. 3 is a measurement period and air measurement. FIG. 4 is an explanatory diagram showing an example of measurement of the relationship between the oxygen utilization rate measurement value and the indicated variation of the oxygen utilization rate measurement value, and FIG. 4 is a system diagram showing another embodiment of the present invention. 1...Aeration 4'K 2121.44...Measuring container 3...Dissolved oxygen measuring device 4,5...Opening/closing valve 6...Rotor 7...Stern 8.22
．．・l (vapor phase air supply port 9, to, 24.27, 29.30... air supply valve 1
2, 26... Air supply device 13... Dissolved oxygen measuring device 14.35... Arithmetic processor 15.34...
Process controller 23...Cleaning air supply ports 25.28, 31.32...Flow rate regulator 33...Oxygen measuring device 36...Correction value calculator 41.42...
・Strainer 43...Air supply port for aeration and cleaning (7317)
Agent Patent Attorney Kensuke Chika (and 1 other person) 1st
Figure 2 Figure 3 Figure 4

Claims (4)

[Claims] (1) A measurement container that is immersed in a solution and has an air supply port for aeration and cleaning at the bottom, an on-off valve mounted on the top and bottom of this measurement container, and a measurement container that is installed so as to be in contact with the sample water in the measurement container. an oxygen meter that measures dissolved oxygen in a solution or partial pressure of oxygen in a gas from the signal from the dissolved oxygen electrode; Process control that performs control that includes a supply process: A correction value is calculated from the ratio of the signal from the oxygen measuring device with air being supplied to the measuring container and the known partial pressure of oxygen in the air stored in advance. An oxygen utilization rate measuring device comprising: a correction value calculator for calculating; and an arithmetic processor for calculating the oxygen utilization rate while correcting it based on a signal from the correction value calculator. (2) The oxygen utilization rate measuring device according to claim 1, wherein the air supply amount from the aeration air supply port and the cleaning air supply port are set to be different. (3) The oxygen utilization rate measuring device according to claims 1 and 2, characterized in that an aeration and cleaning air supply port used for both aeration and cleaning is provided in the lower part of the measurement container. (4) Oxygen utilization rate measurement according to any one of claims 2 and 3, characterized in that the on-off valves provided above and below the measurement container are provided with external strainers. Device.