JPH0731189B2 - Respiration rate measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to fields such as sanitary engineering and fermentation engineering using microorganisms under aerobic conditions such as a sewage treatment system by an activated sludge method. The present invention relates to a method for measuring a respiration rate of microorganisms for performing operation management suitable for a desired purpose.

B. SUMMARY OF THE INVENTION The present invention is a respiratory rate measuring method for calculating a respiratory rate of microorganisms under aerobic conditions such as a sewage treatment system using activated sludge from a dissolved oxygen consumption curve using a respiratory rate converter. At, the respiration rate converter detects the inflection point of the dissolved oxygen consumption curve and sets the range that can be approximated to a straight line.
The approximate linear equation is calculated using the dissolved oxygen consumption data in that range, and the respiratory rate is calculated by its slope, which makes it possible to obtain an accurate respiratory rate even with water quality that gives a dissolved oxygen consumption curve with a bending line. Can be calculated and output.

C. Conventional technology Taking the case of a sewage treatment system using the activated sludge method as an example, activated sludge microorganisms generate oxygen during the process of oxidative decomposition of the stored substances accumulated in the substrate and cells in the inflowing wastewater. Consume. Since this oxygen consumption is used to supply the energy necessary for the growth and life support of microorganisms, it is necessary to accurately grasp the oxygen consumption, that is, the respiration rate, in order to properly operate and manage the activated sludge process. Is very important in.

Next, a conventional device for automatically measuring the respiration rate of activated sludge will be described with reference to FIG. As shown in FIG. 4, the respiration measuring device has a detecting unit 3 immersed in a gas chamber 1.
And the respiratory rate measuring step shown in FIG. As shown in FIG. 5, the detection unit main body 3a has a water intake port 4 at its lower end.
Has a detection discharge port 5 at the upper end. Further, an electrode (hereinafter referred to as a DO (dissolned oxygen) electrode) 16 and a rotating shaft 25, which penetrates the peripheral wall of the main body inside and outside, for measuring the dissolved oxygen concentration, and a rotary shaft 25 penetrate the main body peripheral wall, and the tip thereof. An agitator 17 having a rotary blade 24 and a drive air pipe 8 are provided in the. The drive air pipe 8 is composed of an aeration air pipe 21, an upper pinch valve air pipe 20, and a lower pinch bar air pipe 22. Further, a measuring tank 23 is formed in the detection unit body 3a, and upper and lower measuring tanks 23 are provided with two pinch valves 19 and 18 which are operated by air pipes 20 and 22, respectively. ing. 6 is a DO signal cable and 7 is a stirrer cable.

Further, as shown in FIG. 4, the control unit 15 connected to the detection unit 3 includes a DO amplifier 9 that amplifies a signal from the DO electrode 16, and a respiratory rate converter 11 that calculates a respiratory rate from the DO signal from the DO amplifier 9.
An instruction / output unit 12 for outputting the calculation result, a sequence control circuit 10 for controlling the measurement process, an electric / pneumatic conversion unit 13 for converting a control signal from the sequence control circuit 10 into a pneumatic signal, The air / air conversion unit 13 and the air source 14 for supplying air to the aeration air tube 8 of the detection unit 3.

Next, the operation of each part will be described with reference to the process chart of FIG.

(1) In the water sampling process, upper and lower pinch valves 19 and 18
Open, and the test water is aerated by the aeration air tube 21 of the detection unit main body 3a, and the test water is taken from the test water suction port 4 by the bubble pump action (air lift pump), and the test water discharge port 5 Better drained.

(2) In the aeration process, the upper pinch valve 19 remains open, the lower pinch valve 18 is closed, and the agitator 17 is used to measure the measuring tank 23.
The test water inside is aerated while stirring, and when the dissolved oxygen concentration of the test water reaches a predetermined concentration (for example, 5 mgO ₂ / l), the next degassing step is performed.

(3) In the degassing step, the upper pinch valve 19 is kept open and the lower pinch valve 18 is kept closed to stop the aeration and stirring and remove the bubbles remaining in the measuring tank 12.

(4) In the measurement process, the DO electrode 16 detects the decrease in the dissolved oxygen concentration while the pinch valves 19 and 18 at the upper and lower parts are closed and the aeration is stopped while stirring the test water in the measuring tank 12. To do.

An example of the detection curve of the dissolved oxygen concentration detected in the above measurement step is shown in FIG. In the same figure, the section indicated by the reference numeral is the dissolved oxygen consumption curve in the measurement process, and assuming that it decreases almost linearly, two preset dissolved oxygen concentrations DO1 (shown by the reference numeral) and DO2 (shown by the reference numeral) are set. If the time T1 (indicated by a sign) and T2 (indicated by a sign) of is measured, the respiration rate is given by the following equation.

(However, the units of DO1 and DO2 are mgO ₂ / l, and the units of T1, T2 are h
And ) The above is the operation of the conventional respiration rate measurement device, the dissolved oxygen curve in the measurement process is detected by the DO electrode 16, and amplified by the DO amplifier 16.
The respiration rate converter 11 calculates the respiration rate according to the above equation (1). Regarding such a respiratory rate measuring device, the applicant of the present invention has previously filed Japanese Patent Application No. 56-1084.
I am applying for No. 39.

D. Problems to be Solved by the Invention The problem of the conventional respiratory rate measuring device lies in the respiratory rate converter 11. That is, the conventional respiratory rate converter 11 applies the equation (1) on the assumption that the dissolved oxygen consumption curve (FIG. 7) in the measurement process decreases almost linearly. However, the dissolved oxygen consumption curve does not always decrease linearly, and depending on the water quality of the aeration tank 1, there may be a bending point in the middle of the dissolved oxygen consumption curve as shown in FIG. Here, when the respiratory rate is calculated by the conventional respiratory rate converter 11, (However, in FIG. 8, T3 is a code, T4 is a code, and T5 is a code), but the true respiration rate is the dissolved oxygen consumption curve (8
Since it is correct to use the slope of the first straight line segment (in the figure), the true respiration rate is Becomes However, in the conventional respiration rate converter, even if there is a bending line, it is ignored, so in the water quality that gives a dissolved oxygen consumption curve with a bending line, the measured respiration rate is always higher than the true respiration rate. It will be a small value. That is, Is.

The present invention proposes a new measuring method provided with a respiratory rate converter invented in order to solve the problems of the conventional respiratory rate measuring method, in which the respiratory rate is calculated from the dissolved oxygen consumption curve. With the goal.

E. Means for Solving the Problems First, the main points of the respiratory rate converter used in the present invention will be described. (1) This respiratory rate converter is dissolved with a bending point as shown in FIG. The oxygen consumption curve has a function of detecting its inflection point and determining a starting point (Fig. 1) TS and an ending point (Fig. 1) TE within a range that can be approximated by a straight line.

(2) Similarly, this breathing rate converter has the above linear approximation range
It has a function to obtain an approximate straight line (in Fig. 1) by the least squares method using the dissolved oxygen consumption data between TS and TE.
If the approximate straight line is expressed by an equation, DO = A + BT (5). However, DO: dissolved oxygen concentration (mgO ₂ / l) A: constant (mgO ₂ / l) B: linear slope (mgO ₂ / lh) T: time (h) Here, the respiration rate of the dissolved oxygen consumption curve is since the slope itself approximation curve (FIG. 1), respiration rate ^{_{(mgO 2 / lh) = -}} B ... (6) next, which in the example of FIG. 8, corresponding to formula (3). Therefore, according to the respiratory rate converter of the present invention, the true respiratory rate can be obtained even when the dissolved oxygen consumption curve has a bending point.

Therefore, the present invention, the respiration rate of microorganisms under aerobic conditions such as a sewage treatment system by activated sludge, in the respiration rate measurement method of calculating the respiration rate from the dissolved oxygen consumption curve using a respiration rate converter, Detect the inflection point of the dissolved oxygen consumption curve with a respiratory rate converter, set a range that can be approximated to a straight line, calculate an approximate linear equation using the dissolved oxygen consumption data in that range, and calculate the respiratory rate from the slope. It is a respiratory rate measuring method characterized by the above.

G. Example An example of the present invention will be described with reference to FIGS.

In the respiratory rate converter 11 shown in FIG. 2, when the measurement process is started, the measurement process signal 32 from the sequence control circuit 10 enters the central processing circuit 27 composed of a microcomputer to start the measurement operation. The measurement operation is performed in the following order.

(1) The central processing circuit 27 reads the dissolved oxygen concentration signal 30 from the DO amplifier 9 at a predetermined time interval (generally every 0.1 to 10 seconds), converts it into a digital signal by the A / D conversion circuit 26, and then the storage circuit 28. To memorize. Also, the time data at the time of reading is stored. This process is repeated until the measurement step is completed, and the dissolved oxygen consumption curve data is stored in the memory circuit.

(2) When the measurement process is completed, the central processing circuit 27 determines a range that can be approximated by a straight line from the stored data.

(3) Next, the central processing circuit 27 obtains the equation of the approximate straight line from the dissolved oxygen consumption data in the linear approximation possible range by the calculation of the least squares method, determines the respiratory rate from this slope, and outputs the output circuit.
Output from 29.

Next, a method of determining a range where straight lines can be approximated and a method of calculating approximate straight lines will be described with reference to FIG. Fig. 3 shows the dissolved oxygen consumption curve in the measurement process part. If the starting point DOs in the linear approximation range is the dissolved oxygen concentration of DOs,
The time at that time is Xs. Similarly, the dissolved oxygen concentration at the end point DOe is Ye, the time is Xe, and any point on the curve is
If the data before and after DOn are DOn _-1 DOn ₊₁ respectively, the dissolved oxygen concentration will be YnYn _-1 Yn ₊₁ and the time will be XnXn _-1 Xn ₊₁ respectively. here,
The condition when DOn is within the linear approximation range is Becomes Here, L is the ratio of the slopes of the curves before and after the arbitrary point DOn, and when L = 1, the three points DOn ₋₁ , DO, DOn ₊₁ are on a straight line. However, since the actual dissolved oxygen consumption curve is not a perfect straight line even in the linear approximate range, in the respiratory rate converter 11 according to the present embodiment, Are using. Here, α is a permissible error, and it is empirically preferable to set it between α = 0.01 and α = 0.50 in the measurement of respiratory rate. Therefore, in the measurement process, if the formula (8) is applied while shifting the data one by one from the start of measurement to the end of measurement for all the data stored in the memory circuit 28,
The section in which the equation (8) is continuously satisfied is the linear approximation possible range.

Therefore, in the respiratory rate converter 11 according to the present embodiment, the equation (8) is applied from the measurement start data, and the point DOn that satisfies the equation (8) is first determined as the starting point DOs. Further end point DO
For e, the data immediately before the point that satisfies the following equation after entering the linear approximation range is determined as DOe. That is, Is.

Using the data between DOs and DOe determined by the above method, the least squares method is then used to find the equation of the approximate straight line. That is, the data of dissolved oxygen concentration between DOs and DOe
When Yi, time is Xi, and the number of data is M, the average value of each is given by the following equation.

Next, the product sum Sxy of Xi and Yi is calculated.

Next, calculate the sum of squares Sxx of Xi.

Then, the slope B becomes B = Sxy / Sxx (14), and A is given by A = -B (15). Here, the respiration rate is calculated by the following equation from the equation (6).

Respiration rate _{(mgO 2 / lh) = -} B = - (Sxy / Sxx) ... (16) As is apparent from H. effect the above description of the invention, the conventional respiration rate conversion method, the dissolved oxygen consumption curves measured Although it was not possible to calculate an accurate respiratory rate when measuring a water quality test water having a bending point, according to the respiratory rate conversion method of the present invention, the bending point is detected and a linear approximation is performed. Determine the possible range, calculate an approximate straight line in that range, and from the slope,
Since the respiration rate is calculated, an accurate respiration rate can always be calculated and output.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of respiration measurement, FIG. 2 is an explanatory diagram of a respiratory rate converter according to the present invention, FIG. 3 is a dissolved oxygen consumption curve diagram,
FIG. 4 is an explanatory view of a conventional respiration measuring device, FIG. 5 is a respiration measuring process diagram, FIG. 6 is a detailed sectional view of the main body of the detecting portion, and FIGS. 7 and 8 are detection curves of dissolved oxygen concentration 2 It is a figure which shows two examples. 11 ... Respiratory rate converter, 26 ... A / D conversion circuit, 27 ... Central processing circuit, 28 ... Memory circuit, 29 ... Output circuit, 30 ... Dissolved oxygen concentration signal, 31 ... Respiratory rate output, 32 ... Measuring process signal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-21544 (JP, A) JP-A-58-131519 (JP, A) JP-B-52-23823 (JP, B2)

Claims (1)

[Claims] 1. A respiratory rate measuring method for calculating a respiratory rate under an aerobic condition such as a sewage treatment system using activated sludge from a dissolved oxygen consumption curve using a respiratory rate converter, wherein the respiratory rate is When obtaining the dissolved oxygen consumption curve by the converter, when the measurement process signal is input to the central processing circuit provided in the respiratory rate converter, the dissolved oxygen concentration signal is read,
The signal is stored in the memory circuit together with the time data at the time of reading until the measurement process is completed, and the ratio of the slope of the curve is shifted from the start of the measurement to the end of the measurement with respect to all the data in the stored data. 1 ± α of the expression
(Α: permissible error) After determining the linear approximation possible range that is continuously established, the approximate linear equation is calculated using the dissolved oxygen consumption data in that range, and the respiratory rate is calculated from the slope. Respiratory rate measurement method.