JPS6298256A - Method for measuring respiration speed - Google Patents

Abstract

PURPOSE:To calculate always an exact respiration speed by detecting the inflection point of a dissolved oxygen consumption curve by a respiration speed converter, setting the range where linear approximation is possible, calculating an equation for an approximate straight line by using the data on the dissolved oxygen consumption in said range and calculating the respiration speed by the inclination of said line. CONSTITUTION:A measurement stage signal 32 enters a central processing circuit 27 and a measurement action is started in the respiration speed converter 11. The circuit 27 reads the dissolved oxygen concn. signal 30 from a DO amplifier at prescribed time intervals, converts 26 the signal to a digital signal and stores 28 the signal. The time data in the stage of reading is also stored 28. Such process is repeated until the measurement stage ends and the data on the dissolved oxygen consumption curve is stored 28. The circuit 27 determines the range where the data can be linearly approximated from the stored data upon ending of the measurement circuit and determines the equation for the approximate straight line by the calculation of a method of least squares. The respiration speed is determined from the inclination of said straight line and is outputted 29.

Description

DETAILED DESCRIPTION OF THE INVENTION Fields of application in AJk industry The present invention is applicable to fields such as sanitary engineering and fermentation engineering that use 0* organisms under aerobic conditions, such as sewage treatment systems using activated sludge methods. This invention relates to a method for measuring the respiration rate of microorganisms in order to carry out operational management that meets desired objectives.

B1 Part A of the Invention The present invention is a respiration rate measuring method for calculating the respiration rate of microorganisms under aerobic conditions such as in a sewage treatment system using activated sludge from a dissolved oxygen consumption curve using a respiration rate converter. , detect the bending point of the dissolved oxygen consumption curve using a respiration rate converter, set the range that can be approximated by a straight line,
The feature is that an approximate linear equation is calculated using the dissolved oxygen consumption data in that range, and the respiration rate is calculated from the slope of the equation.This allows accurate respiration rate even in water conditions that give a dissolved oxygen consumption curve with a curved line. can be calculated and output.

C0 Conventional technology Taking the case of a sewage treatment system using the activated sludge method as an example, activated sludge microorganisms consume oxygen in the process of oxidizing and decomposing substrates in influent wastewater and stored substances accumulated in cells. do. Accurately understanding this consumption amount, or respiration rate, is extremely important for proper operation and management of the activated sludge process.7 Next, we will introduce a conventional device that automatically measures the respiration rate of activated sludge. This will be explained with reference to FIG.

The respiration measuring device consists of a detection section 3 immersed in an aeration tank 1 as shown in FIG. 4, and a respiration rate measuring step shown in FIG. As shown in FIG. 5, the main body 3a of the detection section has a test water inlet at the lower end and a detection outlet 5 at the upper end.

Furthermore, an electrode (hereinafter p Q (di
A rotating shaft S passes through the peripheral wall of the main body, and a stirrer having a rotary blade φ and a driving air pipe T are provided at the tip thereof. The drive air pipe t consists of an air pipe for air layer 1, an upper pinch pulp air pipe 0, and a lower pinch pulp air pipe ko. Furthermore, a measurement tank 23 is provided inside the detection unit main body 3a.
At the same time, air pipes 2 are formed in the upper and lower parts of the measuring tank 3.
It is equipped with two pinch pulp decoders, an upper one and a lower one, which are operated by 0 and 2. In addition, 6 is a DO signal cable, and 7 is a knurple for the stirrer.

In addition, as shown in FIG. 4, the control unit /3 connected to the detection unit 3 includes a Do amplifier t that amplifies the signal from the Do electrode 16, and a respiration rate converter that calculates the respiration rate by multiplying the DO signal by the DO amplifier d. 1, an instruction for outputting the calculated results, an output section 1, and a sequence control circuit I for controlling the measurement process.
O, an electric/pneumatic converter 13 that converts a control signal from the sequence control circuit 10 into a pneumatic signal, and a t/pneumatic converter 13.
and an air source L which supplies air to the air layer t of the detection unit 3.

Next, the operation of each part will be explained according to the process diagram shown in FIG.

(1) In the water sampling process, the upper and lower pinch pulp/
9. Open it and open the air pipe 2l of the detection unit main body 3a.
The test water is exposed during the test, and the test water is sampled from the test water suction port S by the action of the air bubble pump (air lift pump) and drained from the test water discharge port S.

(2) In the aeration process, the upper pinch pulp/9 is opened and the lower pinch pulp/l is closed, and the test water in the measurement right column 3 is stirred using the stirrer I, and then air is removed. If the dissolved oxygen concentration of the sample water is a predetermined concentration (for example, 5mg0t/j
), move on to the next degassing process.

(3) In the degassing process, the upper pinch pulp/? is open.

The lower pinch pulp 11 stops blowing and stirring until the closing point t, and air bubbles remaining in the measuring tank 1 are removed.

(4) In the measurement process, pinch pulp/? ,
# is closed, and while stirring the test water in Measurement@/2 with the aeration stopped, a decrease in the dissolved oxygen concentration is detected with the Do electrode 16.

FIG. 7 shows an example of a detection curve of the dissolved oxygen concentration detected in the above measurement step. In the same figure, the section indicated by the symbol ■ is the dissolved oxygen consumption curve in the measurement process, and assuming that it decreases almost linearly, the two preset dissolved oxygen concentrations D01 (indicated by the symbol ■) and DO2 (indicated by the symbol Time Tl (indicated by symbol ■) and T2 (indicated by symbol [stock])
], the respiration rate is given by the following formula.

(However, on DOl and DO2OO2 "gos/'%Tl
, T2 have units of h. ) The above is the operation of the conventional respiration rate measuring device, in which the dissolved oxygen curve in the measurement process is detected by the DO electrode 16, amplified by the amplifier 16, and respiration rate converter // ) The respiration rate is calculated using the equation 0.The applicant of the present application previously filed an application for such a respiration rate measuring device as Utility Model Application No. 108439/1983.

D0 Problems to be solved by the invention Problems with conventional respiration rate measuring devices are respiration rate converters.
It is in. That is, in the conventional respiration rate converter II, (1) II is applied on the assumption that the dissolved oxygen consumption curve (■ in FIG. 7) decreases approximately linearly during the measurement process. However, the dissolved oxygen consumption curve does not always decrease linearly, and depending on the ice 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 respiration rate is determined using a conventional respiration rate converter, DO
I-DO2 Respiration rate = □ ...(2) 4-TS (However, in Fig. 8, TS is indicated by the symbol ■, T4 is indicated by the symbol [phase], and TS is indicated by the symbol ■), but this is true. It is correct to assume that the respiration rate is the slope of the first straight section of the dissolved oxygen consumption curve (Fig. 8), so the true respiration rate is So,
If the water quality gives a curved dissolved oxygen consumption curve, the measured respiration rate will always be less than the true respiration rate, since any bending curve will be ignored. That is, .

The present invention aims to solve the problems of the respiration rate converter that calculates the respiration rate from the dissolved oxygen consumption curve in the conventional respiration rate measurement method. With the goal.

Means for Solving the E0 Problem First, the main points of the respiration rate converter used in the present invention will be described. Detect the inflection point of the oxygen consumption curve and find the starting point of the range that can be approximated by a straight line (■ in Figure 1) T
It has the function of determining S and the end point (■ in Figure 1) TE.

(2) Similarly, this respiration rate converter has the above linear approximation range 1.
It has the function of calculating the approximate straight line 1IJ (in Figure 1) by the least squares method using the dissolved oxygen consumption data between fflTs and TE.If the approximate straight line is expressed by the formula, DO=A+B
T...(5) becomes. Just in case DO: Dissolved oxygen concentration (mgol/1) A: Constant (m
go snow/1) B: Slope of straight line (mg/-', b) T: Time (h
) Here, the respiration rate of the dissolved oxygen consumption curve is the approximation surface 1jl
(Figure 1) Since this is the slope itself, the respiration rate (m
g01/j, h) = -B = 16),
In the example of FIG. 8, this corresponds to equation (3). Therefore, according to the respiration rate converter of the present invention, the true respiration rate can be determined even when the dissolved oxygen consumption curve has an inflection point.

Therefore, the present invention provides a method for measuring the respiration rate of microorganisms under aerobic conditions such as in a sewage treatment system using activated sludge, in which the respiration rate is calculated from a dissolved oxygen consumption curve using a respiration rate converter. Detect the bending point of the dissolved oxygen consumption curve using a respiration rate converter, set the range where a straight line can be approximated, calculate the approximate linear equation using the dissolved oxygen consumption data in that range, and calculate the respiration rate from the slope of the approximate linear equation. This is a respiration rate measuring method characterized by the following.

G. Embodiment An embodiment of the present invention will be described based on FIGS. 1 to 3.

In the respiration rate converter/l shown in FIG. 2, when the measurement process begins, a measurement process signal 32 is sent from the sequence control circuit 10 to the micro combinatorial central processing circuit to start the measurement operation. The measurement operation is performed in the following order.

(1) The central processing circuit reads the dissolved oxygen concentration signal 30 from the DO amplifier 9 at predetermined time intervals (generally every 0.1 seconds to 10 seconds), converts it into a digital signal using the A/D conversion circuit, and then stores it. Store it in the circuit. It also stores time data at the time of reading. This process is repeated until the measurement process is completed, and the data of the dissolved oxygen consumption curve is stored in the storage circuit.

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

(3) Next, the central processing circuit core calculates the equation of an approximate straight line using the least squares method based on the dissolved oxygen consumption data in the range that can be approximated by a straight line, determines the respiration rate from this slope, and outputs it from the output circuit knob. .

Next, a method for determining the range that can be approximated by a straight line and a method for calculating the approximate straight line will be explained with reference to FIG. Figure 3 shows the dissolved oxygen consumption curve in the measurement process.If the starting point of the linear approximation range is po8@, then the dissolved acid odor concentration of Do s@ is 'fs■The time at that time is X8■. ◇Similarly, the dissolved oxygen concentration at the end point DOe■ is set as Ye■, and the time as Xe■
, Furthermore, if an arbitrary point on the curve is Don@ and the data before and after it are DOn-+ @ t■ in DOn, then the dissolved oxygen concentration is Yn■ Y n-+■ Y
n + I■, and the time is Xn■ xn, respectively.
-t■Xn+1 [shares]. Here, the conditions when DOn is within the linear approximation range are as follows. Here, L is the ratio of the slopes of the curves before and after an arbitrary point Don, and when L=1, 'i DOn -r,
D.O.

The three points IDn+t are on a straight line. However, since the actual dissolved oxygen consumption curve is not a perfect straight line even within the range where linear approximation is possible, the following is used in the respiration rate converter/l according to this embodiment. Here, α is a permissible error, and based on experience, it is best to set it between α = 0.01 and α = 0.50 for respiratory rate measurement. Therefore, in the measurement process,
When formula (8) is applied to all data stored in the memory circuit t while shifting the data one by one from the start of measurement to the end of measurement, the range where formula (8) is continuously satisfied is the range in which linear approximation is possible. It is.

Therefore, in the respiration rate converter// according to the present embodiment, Equation (8) is applied from the data at the start of measurement, and the point Don that satisfies Equation (8) is first determined as the starting point DOs. Furthermore, the end point DOe is determined to be the data immediately before the point that satisfies the following equation for the first time after entering the linear approximation range. That is, .

Using the data between DOa and DOe determined by the above method, the equation of the approximate straight line is then determined using the least squares method. That is, assuming that the data of dissolved oxygen concentration between DOa and DOa is Yi9 hours is Xi and the number of data is M, the sum of products Sxy of Xi and Yi is calculated after each average.

Next, the sum of squares Sxx of Xt is calculated.

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

Call@speed(mgox/'-h)=-B=-(Sxy/5
xx) ...Effects of the asH0 Invention As is clear from the above explanation, the conventional respiration rate conversion method is not accurate when measuring water quality where the measured dissolved oxygen consumption curve has an inflection point. However, according to the respiration rate conversion method according to the present invention, a bending point is detected, a range where a straight line can be approximated is determined, an approximate straight line within that range is calculated, and its slope is calculated. Than,
Since the respiration rate is calculated, it is possible to always calculate and output an accurate respiration rate.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a respiration measurement example, FIG. 2 is an explanatory diagram of a respiration rate converter according to the present invention, and FIG. 3 is a dissolved oxygen consumption curve diagram.
Fig. 4 is an explanatory diagram of a conventional respiration measurement device, Fig. 5 is a diagram of the Fi respiration measurement process, Fig. 6 is a detailed view of the h-plane of the main body of the detection unit, and Figs. 7 and 8 are the detection curve of dissolved oxygen concentration. It is a figure which shows two examples. 7i...Respiration rate converter, Kob...A/D conversion circuit, Core...Central processing circuit, Koto...Memory circuit, Kot...
...Output circuit, 30...Dissolved oxygen concentration signal, 31...
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Claims (1)

[Claims] (1) In a respiration rate measurement method in which the respiration rate of microorganisms under aerobic conditions, such as in a sewage treatment system using activated sludge, is calculated from a dissolved oxygen consumption curve using a respiration rate converter, respiration rate conversion is performed. The device detects the bending point of the dissolved oxygen consumption curve, sets the range where a straight line can be approximated, calculates the approximate linear equation using the dissolved oxygen consumption data in that range, and calculates the respiration rate from the slope. A method for measuring respiration rate.