JPH09297132A - Microorganism respiration velocimeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microorganism respiration velocimeter that can calibrate the detection value of an oxygen sensor abreast of measurement of respiration velocity. SOLUTION: A specified quantity of a sample solution containing BOD substrate is charged in a first closed vessel 1, and circulating aeration is started. Air blown into the solution from a diffusion pipe 6 is blown into a second closed vessel 1 from an upper part of the first closed vessel 1 through a pipeline 8, and CO2 contained in the air is absorbed into a KOH solution. A detected oxygen concentration signal of an. Oxygen sensor 3 is inputted to a data processor 5 where the initial oxygen concentration value is computed and stored. After the lapse of specified time, an oxygen concentration signal of the oxygen sensor 3 is inputted again to the data processor 5 so as to compute the oxygen concentration value at this time. The oxygen consumption is obtained from the difference between this oxygen concentration value and the initial oxygen concentration value to compute the respiration velocity of microorganisms. The volumetric decrease quantity of a closed loop system obtained by a level sensor is made the true value, and the volumetric decrease quantity obtained by a detection signal of the oxygen sensor 3 is calibrated on the basis of this true value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a respiration rate meter for measuring the respiration rate of microorganisms by detecting the oxygen consumption of microorganisms utilizing oxygen such as BOD-assimilating bacteria and nitrifying bacteria with an oxygen sensor, and more particularly to an oxygen sensor. The present invention relates to a respiration rate meter for microorganisms equipped with a mechanism for calibrating the respiration rate calculated from the detection signal.

[0002]

2. Description of the Related Art An example of a conventional device for measuring the respiration rate of microorganisms will be described with reference to FIG.

This measuring device has a first closed tank (measurement tank).
1, a second closed tank (CO ₂ absorption tank) 2, an oxygen sensor 3,
It is composed of an air pump 4, a data processing device 5, and the like. The first closed tank 1 is provided with an air diffuser 6 and a sample injection valve 7. The gas in the upper part of the first closed tank 1 is transferred to the second closed tank 2
The pipe 8 is provided so as to be blown into the alkaline solution (for example, KOH solution), and the pipe 9 is provided so as to supply the gas in the upper part of the second closed tank 2 to the diffuser pipe 8. An oxygen sensor 3 and an air pump 4 are provided in the middle of the pipe 9.
Is provided. Although not shown, the pipes 8 or 9 are provided with an atmosphere release valve in order to replace the gas in the closed tanks 1 and 2 and the pipes 8 and 9 with fresh air.

In order to measure the respiration rate of microorganisms contained in the sample, a liquid containing activated sludge is stored in the first closed tank 1 and the alkaline solution (in this case, KOH solution) is stored.

Next, a predetermined amount of the sample solution containing the BOD substrate is introduced into the first closed tank 1 via the sample injection valve 7. After closing the sample injection valve 7, air is sent to the liquid phase of the first closed tank 1 by the air pump 4, and circulation aeration is started. The air blown into the liquid from the air diffuser 6 is the first closed tank 1
CO ₂ contained in the air is absorbed into the KOH solution by being blown into the second closed tank 2 through the pipe 8 from the upper part of the. The air floating above the KOH solution is blown again into the liquid in the first closed tank 1 through the pipe 9. This piping 9
When passing through, the oxygen sensor 3 senses the O ₂ concentration in the air. After the noise at the time of starting the air pump 4 is attenuated, the oxygen concentration signal detected by the oxygen sensor 3 is input to the data processing device 5, and the initial oxygen concentration value is calculated and stored.
After a predetermined time has elapsed, the oxygen concentration signal of the oxygen sensor 3 is input again to the data processing device, and the oxygen concentration value at this time is calculated. The oxygen consumption is determined from the difference between the oxygen concentration value and the initial oxygen concentration value, and the respiration rate of the microorganism is calculated.

[0006]

As described above, the oxygen concentration in the air circulating in the closed loop is measured by using the oxygen sensor 3, and the respiration rate of the microorganism is determined from the measured value. It is necessary to compare the detection signal value of 1 with the true value and perform calibration so that the true value is obtained.

Conventionally, when performing this calibration, a known amount of BO
The D substrate is put into the first closed tank, the oxygen consumption is measured by the oxygen sensor 3, the theoretical consumption of oxygen by the known amount of BOD substrate is calculated, and the oxygen consumption is detected by the theoretical oxygen consumption as a true value. Although the oxygen concentration was calibrated, the actual respiration rate measurement was interrupted, the frequency of calibration decreased, and the measurement frequency tended to decrease.

It is an object of the present invention to provide a microbial respirometer capable of calibrating an oxygen sensor detection value in parallel with respiration rate measurement.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a first closed tank for containing active sludge and BOD substrate-containing water,
A second sealed tank containing an alkaline solution and the gas in the upper part of the first sealed tank are blown into the alkaline solution in the second sealed tank, and the gas in the upper part of the second sealed tank is discharged. A circulation device for blowing into the sludge mixed liquid in the first closed tank, an upper part in the first closed tank, an upper part in the second closed tank and the circulation device. An oxygen sensor for detecting the oxygen concentration in the closed loop, a detection means for detecting the volume or pressure of the gas in the closed loop, and the respiration of microorganisms in the first closed tank from the change with time of the output signal from the oxygen sensor. Respiratory rate calculating means for calculating a velocity, a first oxygen concentration change amount obtained from a change with time of an output signal of the oxygen sensor, and a second amount obtained from a change with time of an output signal from the volume or pressure detecting means. Calibration ratio to calculate the ratio with the oxygen concentration change amount of And a computing means, in which the calibration ratio from the calculating means of said calibration ratio is characterized in that so as to calibrate the enter breathing rate to the respiratory rate calculating means.

In the microbial respiratory rate meter of the present invention,
Oxygen consumption obtained from the oxygen concentration detection value of the oxygen sensor,
Since the calibration is performed by the oxygen consumption obtained from the volume or pressure of the gas in the closed loop, the oxygen sensor detection signal can be calibrated in parallel with the actual respiration rate measurement.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 (a) is a system diagram of a microorganism respiration rate meter according to an embodiment, in which a gas volume change amount is measured in a portion of a pipe 9 in the immediate vicinity of a second closed tank 2. Bowl 10
Are connected via a pipe 11. This measuring instrument 10
Includes a closed container 12, a straight pipe 13 inserted into the container 12, and a level sensor 14 provided at a lower portion of the straight pipe 13 for measuring the water level in the straight pipe 13. The upper end of the straight pipe 13 is open to the atmosphere, and the lower end is open to the water in the container 12. The detection signal of the level sensor 14 is input to the data processing device 5.

The other structure of the respiration rate meter for this microorganism is the same as that shown in FIG. 1 (b).

In the microorganism respiration rate meter thus constructed, the respiration rate of the microorganism is measured by the same procedure as in the case of FIG. 1B, and the detection signal of the oxygen sensor 3 is sent to the data processing device 5. In addition to the input, the detection signal of the level sensor 14 is also input to the data processing device 5.

In the data processing device 5, the level sensor 14
The volume reduction amount of the closed loop system obtained by is set as a true value, and the volume reduction amount obtained by the detection signal of the oxygen sensor 3 is calibrated based on the true value.

The oxygen sensor 3 is calibrated using the detected value of the gas volume change measuring device 10 periodically.

The specific calculation method of the calibration is as follows.

The initial output value of the oxygen sensor 3 (the output voltage indicating the initial oxygen concentration) is E _1, and the output voltage at the end of the measurement is E ₂ . The output voltage of the oxygen sensor 3 is linearly proportional to the oxygen concentration, and therefore the amount of oxygen consumed by the respiration of microorganisms is multiplied by a constant coefficient k with respect to the difference between the output voltages E ₁ and E _2. It will be a value.

Therefore, the oxygen concentration change ΔC _S (%) calculated from the output voltage of the oxygen sensor 3 is expressed as ΔC _S = k (E ₁ −E ₂ ) using the coefficient k.

On the other hand, the difference between the initial detected water level of the level sensor 14 of the measuring instrument 10 and the detected water level at the end of measurement is ΔH (c
m), and the horizontal cross-sectional area of the container 12 is S (cm ² ),
When the initial gas volume in the loop is is Q, the oxygen concentration change C _L which is calculated from the output signal of the level sensor 14 is expressed as follows.

ΔC _L = [(ΔH · S) / (Q−ΔH · S)
/ 2)] × 100 The meaning of this formula is [(reduced gas volume) / (average value of gas volume in closed loop)] × 100. In the denominator of this equation, the average of the volume Q at the start of measurement and the volume Q−ΔH · S at the end of measurement [Q + (Q−ΔH · S
S)] × 1/2 = Q−ΔH · S / 2 is used.

Strictly speaking, it is necessary to obtain the oxygen concentration by the oxygen sensor from the corresponding volume from the change in the vapor phase volume during the measurement, but here, as a simple method, the intermediate value of the vapor phase volume is used for the calculation. I decided. With this method, even if there is an offset in the measured value of the oxygen sensor, it does not affect the result. Further, the change in the dissolved oxygen concentration in the liquid phase is negligible because it is very small as compared with the oxygen concentration in the gas phase.

This ΔC _L is used as a true value to calibrate ΔC _S. For that purpose, the coefficient k up to that time is k × (Δ
What is necessary is just to replace it with a new coefficient of C _L / ΔC _S ).

As described above, it becomes possible to calibrate the coefficient k periodically, obtain a highly accurate oxygen consumption amount, and measure the respiratory rate with high accuracy. In the present invention, it is preferable that the calibration is performed successively while the respiration rate of each measurement sample at each time point is continuously measured.

Although the oxygen sensor is calibrated by measuring the gas volume change in the closed loop system in the above embodiment, the oxygen sensor may be calibrated by measuring the gas pressure change in the closed loop system.

[0025]

As described above, according to the present invention, the detection value of the oxygen sensor can be calibrated for each measurement, and the accuracy can always be maintained. Further, if calibration calculation and coefficient correction processing are incorporated in the calculation software of the data processing device, the calibration can be performed automatically, so that no special effort is required for the calibration. Therefore, according to the present invention, the respiration rate of oxygen-using microorganisms such as BOD-assimilating bacteria and nitrifying bacteria can be measured with high accuracy.

[Brief description of drawings]

FIG. 1A is a system diagram of a respiration rate meter for microorganisms according to an embodiment. FIG. 1B is a system diagram of a respiration rate meter for microorganisms according to a conventional example.

[Explanation of symbols]

1 First closed tank (measurement tank) 2 Second closed tank (CO ₂ absorption tank) 3 Oxygen sensor 4 Air pump 5 Data processing device 6 Diffuser tube 7 Sample injection valve 10 Gas volume change measuring instrument 12 Container 13 Straight tube 14 Level sensor

Claims (1)

[Claims] 1. A first closed tank for containing activated sludge having activity and BOD substrate-containing water, a second closed tank for containing an alkaline solution, and an upper gas in the first closed tank. A circulation device for blowing the alkaline solution in the second closed tank into the sludge mixed solution in the first closed tank while blowing the gas in the upper part of the second closed tank; An oxygen sensor for detecting an oxygen concentration in a closed loop composed of an upper part in the closed tank, an upper part in the second closed tank and the circulation device, and an oxygen sensor for detecting the volume or pressure of gas in the closed loop. A detecting means; a respiratory rate calculating means for calculating a respiratory rate of microorganisms in the first sealed tank from a change with time of an output signal from the oxygen sensor; and a first obtained from a change with time of an output signal of the oxygen sensor.
Of the oxygen concentration change amount and a second oxygen concentration change amount obtained from the time-dependent change of the output signal from the volume or pressure detecting unit, and a calibration ratio calculating unit for calculating the ratio. A respiration rate meter for microorganisms, characterized in that a recalibration rate is input to the respiration rate calculation means to calibrate the respiration rate.