JPH05164679A - Calibration method of sludge densitometer - Google Patents

Abstract

PURPOSE:To simplify the calibration of a sludge densitometer and to eliminate the discontinuity of measuring values due to the calibration. CONSTITUTION:In this sludge densitometer, an operating value M corresponding to the density of sludge is obtained from the intensity of the scattering light when the light is cast to a processed water of sludge. A measuring value S of the density of sludge is obtained from a calibration curve representing the corresponding relationship between the operating value M and the analyzing value of the density of sludge. A calibration curve is obtained from N data selected among the first analyzing value S0 and the corresponding operating value M0, and previous analyzing values S1, S2,... and the corresponding operating values M1, M2,....

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calibrating an optical sludge concentration meter used in sewage treatment and the like.

[0002]

2. Description of the Related Art In order to treat sewage by an activated sludge method or the like, it is necessary to measure the amount of organic substances and the sludge concentration and sludge flow rate are measured.

As the sludge densitometer, an optical type and an ultrasonic type are known. In the optical type, the sludge concentration is calculated by irradiating the treated water with light and calculating the intensity of scattered light from the suspended matter. Ultrasound is used instead of light.

FIG. 4 shows a block diagram of a sludge concentration meter. 1
The two light sources 1 irradiate the treated water with light, and the two light receivers 2 ₁ and 2 ₂ having different distances from the light source 1 receive the scattered light from the suspended matter and detect the light receivers 2 ₁ and 2 ₂ . The signals are amplified by the amplifiers 3 ₁ and 3 ₂ , respectively, and the calculation unit 4 obtains the concentration from the received light intensity.

In this structure, the received light intensities I ₁ and I ₂ received by the light receivers 2 ₁ and 2 ₂ are expressed by the following equations.

I ₁ = I ₀ · S · exp (−β ₁ · S) ... (1) I ₂ = I ₀ · S · exp (−β ₂ · S) ... (2) where I ₀ : of the light source Light intensity S: Concentration of suspended matter β ₁ , β ₂ : Constant determined by the distance between the light source and the light receiving position.
Is a function having an extreme value, for example, I ₁
The intensity output has two values of suspended matter concentrations S ₁ and S ₂ , and the concentration cannot be determined by measuring scattered light with one light receiver.

Therefore, the detection system of the two photodetectors 2 ₁ and 2 ₂ is provided, and the natural logarithm of the ratio of the above equations (1) and (2) is obtained. Ln (I ₂ / I ₁ ) = ln (exp (Β ₁ −β ₂ ) · S) = (β ₁ −β ₂ ) · S (3), and a unique received-light intensity signal can be obtained for the operation unit 4 with respect to the suspended matter concentration S.

As another calculation method, the signals I ₁ , I ₂
From I ₂ ² / I ₁ = I ₀ · S · exp (β ₁ -2β ₂ ) S (4) where I ₀ is a proportional constant and the arrangement of the photodetectors 2 ₁ and 2 ₂ is adjusted appropriately. By doing so, (β ₁ −2β ₂ ) = 0 is set, and a unique density signal is obtained.

As described above, the sludge densitometer can obtain an output having a linear relationship with the concentration of suspended solids, but its proportional constant changes depending on the change in the property of sludge,
It is necessary to calibrate regularly or according to the season.

Changes in the properties of sludge include changes in sludge color, changes in sludge particle size distribution, changes in sludge specific gravity, and the like.

The conventional calibration method for a sludge densitometer is performed by the procedure shown in FIG.

(1) Sampling: The detector consisting of the photo detectors 2 ₁ and 2 ₂ and the amplifiers 3 ₁ and 3 ₂ is removed from the position of the measuring section,
Sludge is collected, concentrated, and diluted from the sludge pipe, sludge of several kinds of concentrations is adjusted, the detection unit is immersed in the sludge of each concentration, and the measured values M ₁ , M _{2 at} that time are recorded, and the detection unit is detected. Return to the measuring position.

(2) Analysis: Concentrations S ₁ , S ₂ , ... Are obtained by manual analysis for each concentration of sludge.

(3) Creation of calibration curve ... Each measured value M ₁ , M ₂ ,
A calibration curve (shown in FIG. 7) is created from ... And the analysis values S ₁ , S ₂ ,.

(4) Calculation of gain: The gain (slope), which is the ratio of the output of the densitometer to the analysis value of the concentration, is obtained from the calibration curve by the method of least squares.

(5) Correction of gain: The densitometer output gain is corrected from the obtained gain.

Such a calibration is performed at the start of measurement, when it seems that the sludge properties have changed, and at regular intervals.

[0018]

The conventional calibration method has the following problems.

(1) The measurement of the concentration is interrupted during the sampling work, and when the detecting portion is installed in the mud pipe having a pressure, it is necessary to remove the detecting portion and operate the valve to operate the valve, which is complicated. It will be a task.

(2) Since manual analysis involves steps such as sludge drying, one sample requires several hours of work, which requires calibration for a long period of time, and the cost thereof increases.

(3) In the period from the start to the end of calibration, inaccurate measurement data may be entered or the measurement data may be discontinuous.

Although it is possible to automatically perform the processing from the creation of the calibration curve to the correction of the gain, the above-mentioned problems have hardly been solved.

An object of the present invention is to provide a calibration method that simplifies the calibration of a sludge concentration meter and eliminates the discontinuity of the measured values due to the calibration.

[0024]

In order to solve the above-mentioned problems, the present invention obtains a calculated value M corresponding to the sludge concentration from the light irradiation to the sludge treated water and the scattered light intensity, and the calculated value M and the sludge. In a sludge densitometer for obtaining a measured value S of sludge concentration from a calibration curve having a correspondence relationship with the concentration analysis value, a concentration analysis value S ₀ is obtained by analyzing a sample by sampling sludge treated water, and the calculated value at the time of sampling is obtained. M ₀ is obtained, and the plurality of concentration analysis values S ₁ , S obtained in the past are obtained.
_2, ... and the calculated value M _1, M _2, setting the number of the order of N concentration analysis values closer to the concentration analysis value S ₀ from ... data S _1, S _2, ...
S _N and the calculated values M ₁ , M ₂ , ... Corresponding to the respective concentration analysis values
It is characterized in that M _N is selected and the calibration curve is obtained from the selected concentration analysis value and calculated value and the analysis value S ₀ and calculated value M ₀ .

[0025]

Function Calibration for creating and setting a calibration curve from the analytical value S _{0 obtained} by sampling sludge treated water, the calculated value M _{0 at} that time, and past data S ₁ , S ₂ , ... And M ₁ , M ₂ ,. As a method, one sample is used for sampling and analysis, and a calibration curve is obtained by using analysis data obtained in the past calibration. Further, by using the past data, the sudden change of the calibration curve, that is, the discontinuity of the measured value due to the calibration is eliminated.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention. Sludge treated water is sent to the sludge pipe 11, and the sludge pipe 1
1, a light scattering light type detection unit 12 is attached, and a sampling port 13 for collecting a sample of treated water
Is provided.

The detection signal from the detection unit 12 is supplied to the calculation of the above-mentioned formula (3) or (4) by the first calculation unit 14, and the calculation value M corresponding to the suspended substance S is given to the calculation unit 14. obtain.

The second calculation unit 15 obtains the concentration S as a measured value from the relationship with the concentration S of suspended solids by using the gain calibrated with respect to the calculation value M from the first calculation unit 14.

The calibration unit 16 obtains a calibration curve by receiving the calibration calculation data and updates the gain of the calculation unit 15. The calibration calculation data includes suspended matter concentrations S ₁ , S ₂ , by analysis of sample treated water from the sampling port 13.
... and the outputs M ₁ , M ₂ , of the calculation unit 14 at the time of sampling
... and an appropriate data number set value N are given.

The calibration procedure by the calibration unit 16 is shown in FIG.

(1) Sampling: A sample is taken from the sampling port 13 while the sludge treated water is flowing, and the output M ₀ of the computing unit at that time is read. (2) Analysis: The sample is analyzed to determine the concentration S ₀ of suspended solids. Ask.

(3) Setting of the number of data N ... The calibration unit stores data M ₁ , M ₂ , ... M _n at the time of calibration performed in the past and data S ₁ , S ₂ , ... S _n corresponding thereto. The number N of data to be used for this calibration is determined from among these.

(4) Data selection ... Past data S ₁ ,
S _2, ... rearranges data in ascending order of distance from S _n to the current data S _0, to select the N pieces of data, including the S ₀ from near data to the data S _0.

(5) Calibration curve creation ... The above N data S
_A constituent curve is created from _N and the corresponding data M _N by the least square method.

(6) Setting of new gain ... Gain (inclination) is obtained from the created calibration curve (for example, A and B in FIG. 7) and set in the arithmetic unit 15.

Therefore, the sampling port 13 is used for calibration.
A sample is collected from the sample and the output M _{0 at} that time is read, and a calibration curve is obtained from the analysis values S ₀ and M _{0 of} this sample and the past N pieces of data S _N and M _N by the least square method,
Obtain the calibration curve that is the relationship between the suspended matter concentration and the output M,
By setting the inclination in the calculator 15, the subsequent density measurement value can be obtained.

It should be noted here that the conventional complicated work of removing the detector 12 for calibration is eliminated,
Only one sampling and analysis from the sampling port 13 is required. Further, since the calibration curve is obtained from the sample analysis result S ₀ together with other (N−1) pieces of past sample data together with M _{0 at} that time, the gain up to that time may change rapidly due to the calibration. Moreover, the measurement is continued during the calibration, and the measured values do not become discontinuous.

When it is considered that the property of sludge suddenly changes, the sample collection can be coped with the sudden change of property by repeating the sampling interval at a relatively short time.

The above-described calibration is a simple calibration, and if the simple calibration cannot be handled at the initial stage of measurement or when the measurement conditions change significantly, the precision measurement similar to the conventional one can be performed to maintain the desired measurement accuracy. The processing procedure including this precision calibration is shown in FIG.

[0040]

As described above, according to the present invention, the analytical value S ₀ of the sludge treated water sample, the calculated value M _{0 at} that time, the past analytical values S ₁ , S ₂ , ... And the calculated value M ₁ , M ₂ , ... Since the calibration curve is obtained from the N pieces of data selected, the measurement stop time and the analysis time due to the calibration can be greatly shortened because only one sampling and analysis is required. Moreover, the discontinuity of the measured value after calibration becomes small.

[Brief description of drawings]

FIG. 1 is a device configuration diagram showing an embodiment of the present invention.

FIG. 2 is a calibration procedure diagram of the embodiment.

FIG. 3 is a measurement / calibration procedure diagram of the embodiment.

FIG. 4 is a block diagram of a sludge concentration meter.

FIG. 5 is a scattered light intensity characteristic diagram.

FIG. 6 is a conventional calibration procedure diagram.

FIG. 7 is a characteristic diagram of a calibration curve.

[Explanation of symbols]

12 ... Detection unit, 13 ... Sampling port, 14 ... Arithmetic unit, 15 Arithmetic unit, 16 ... Calibration unit.

Front page continuation (72) Inventor Shigeo Sato 2-17 Osaki, Shinagawa-ku, Tokyo Stock company Shameidensha

Claims (1)

[Claims] 1. The irradiation value of sludge-treated water and the calculated value M corresponding to the sludge concentration are obtained from the scattered light intensity, and the sludge concentration is measured from a calibration curve having a correspondence relationship between the calculated value M and the sludge concentration analysis value. In a sludge densitometer for obtaining the value S, a concentration analysis value S ₀ is obtained by analyzing a sample by sampling sludge treated water, the calculated value M ₀ at the time of the sampling is obtained, and a plurality of the concentration analysis values S obtained in the past are obtained. ₁ , S
_2, ... and the calculated value M _1, M _2, setting the number of the order of N concentration analysis values closer to the concentration analysis value S ₀ from ... data S _1, S _2, ...
S _N and the calculated values M ₁ , M ₂ , ... Corresponding to the respective concentration analysis values
A method for calibrating a sludge densitometer, wherein M _N is selected, and the calibration curve is obtained from the selected concentration analysis value and calculation value, and the analysis value S ₀ and calculation value M ₀ .