CN1967215A - UV scanning type multispectral water-quality COD rapid detection method and device therefor - Google Patents

Abstract

The invention discloses an ultraviolet scanning multi-spectrum water quality COD rapid detection method and a device thereof. The embedded microcomputer system is connected to the single-chip microcomputer system, and the single-chip microcomputer system is connected to the spectrum scanning stepper motor, measuring valve, and cleaning valve in turn. The flow measuring tank is connected to the automatic cleaning device, water sample outlet, cleaning valve, and measuring valve. The cleaning water inlet is connected, the measuring valve is connected with the water sample inlet to be tested, the ultraviolet light emitted by the deuterium light source is converged and passes through the measurement tank, and the ultraviolet light absorbed by the water sample is incident on the plane grating spectroscopic system through converging, and then incident To the photoelectric conversion circuit, the photoelectric conversion circuit is connected with the single-chip microcomputer system. The invention improves the applicability and measurement accuracy of the COD measuring instrument based on ultraviolet absorption; realizes the full automation of water sample extraction, measurement tank cleaning and measurement, improves the speed of online measurement, and can be suitable for environmental water and various types of waste water On-line, fast and accurate analytical test for COD.

Description

Ultraviolet scanning multispectral water quality COD rapid detection method and device

technical field

The invention relates to an ultraviolet scanning multi-spectrum water quality COD rapid detection method and a device thereof.

Background technique

Chemical Oxygen Demand (Chemical Oxygen Demand, COD for short) is a representative indicator of water quality organic matter pollution. In water environment protection and treatment, this parameter is used as a must-test item to characterize the degree of water quality pollution at home and abroad. At present, the measurement methods of COD parameters at home and abroad mainly include: Potassium dichromate method (CODcr method) is used for wastewater, potassium permanganate method (CODMn) is used for surface water, and ultraviolet absorbance method (UV method) can measure wastewater and COD at the same time. surface water. Because the UV method has the advantages of no secondary pollution and fast measurement speed, it has shown a tendency to replace the CODcr method in field measurement. The UV method has relatively mature products abroad, has been widely used in Europe and Japan, and has also been introduced in China, but there is no self-developed ultraviolet full-band UV method COD measuring instrument.

Most foreign UV COD measuring instruments use the absorbance value of a single wavelength of ultraviolet light at 254 (253.7) nm, and convert the COD value by establishing the linear correlation between the 254 nm absorbance value A ₂₅₄ and the COD of different water samples. The reason for choosing 254nm is because it happens to be the main radiation wavelength of the low-pressure mercury lamp. It is theoretically feasible to use the absorbance value of a single ultraviolet light wavelength to convert the COD value, and it can also achieve certain effects in practice for certain water samples with a single and stable component. But in fact, the maximum absorption wavelength of wastewater from different factories and different surface waters is not all at 254nm. Usually, due to the diversity and complexity of water sample components, there are multiple absorption peaks in the ultraviolet band, and the The organic pollutants vary. The linear correlation relationship established with a single absorbance value and COD does not conform to and cannot fully reflect the pollution degree of the water body. The applicability and accuracy of the UV single-band COD measurement method to different water bodies, and the networking of data communication are all restricted. a great restriction.

Contents of the invention

The purpose of the present invention is to provide an ultraviolet scanning multi-spectrum water quality COD fast detection method and its device.

The ultraviolet scanning type multi-spectral water quality COD rapid detection method comprises the following steps:

1) First, scan the water sample in the full range of ultraviolet light from 200nm to 400nm;

2) According to the blank calibration results and scanning results, calculate the absorption spectrum data of the whole ultraviolet band;

3) Obtain multiple characteristic spectra reflecting the organic pollution characteristics of the water body from all the absorbance data;

4) Using these characteristic spectra and corresponding COD values, use BP neural network to establish a correlation model between the two;

5) In the actual water sample measurement, use the measured characteristic spectrum and the established correlation model to quickly invert the COD value of the water sample.

Ultraviolet scanning multi-spectrum water quality COD rapid detection device: the embedded microcomputer system is connected to the single-chip microcomputer system, and the single-chip microcomputer system is connected to the spectral scanning stepper motor, measurement valve, cleaning valve in turn, and the flow measurement tank is connected to the automatic cleaning device, water sample outlet, The cleaning valve is connected with the measuring valve, the cleaning valve is connected with the cleaning water inlet, the measuring valve is connected with the measured water sample inlet, the ultraviolet light emitted by the deuterium light source converges and passes through the measurement tank, and the ultraviolet light absorbed by the water sample passes Convergent and incident to the plane grating light splitting system, after the light is split, it is incident to the photoelectric conversion circuit, and the photoelectric conversion circuit is connected with the single-chip microcomputer system.

The circuit of described embedded microcomputer system is: central processing circuit is connected with RS232 serial interface circuit, RS485 serial interface circuit, touch screen interface circuit, storage circuit, Ethernet communication interface circuit, LCD display interface circuit respectively, wherein LCD display The interface is connected to the 5.7" TFT display screen, and the touch screen interface is connected to the touch screen.

The circuit of the single-chip microcomputer system is: single-chip microcomputer circuit and analog-to-digital conversion circuit, pump valve control circuit, stepper motor control drive circuit 1, stepper motor control drive circuit 2, serial interface circuit connected, stepper motor control drive circuit 1 and The spectral scanning stepper motor is connected, and the stepper motor control drive circuit 2 is connected with the automatic cleaning device.

The ultraviolet multispectral scanning system is composed of a deuterium light source 1, a first converging lens 2, a second converging lens 4, a plane grating beam splitting system, and a silicon photodiode 11, wherein the plane grating beam splitting system is sequentially connected with the incident slit 5 and the collimating objective lens 6 , a plane grating 8, a condenser objective lens 7, a plane grating 8, a stepping motor 9, and an exit slit 10 are connected. Automatic cleaning device is made of stepping motor 13, crankshaft linkage 14, cleaning bar 15, cleaning soft wipe 16.

The present invention improves the applicability and measurement accuracy of the COD measuring instrument due to the adoption of ultraviolet multi-spectrum automatic scanning system, embedded microcomputer system and neural network composition of rapid COD measurement technology; It realizes the full automation of water sample extraction, measurement tank cleaning and the whole measurement process; the contact automatic cleaning device can effectively remove the contamination on the optical window in the flow tank and reduce the measurement error caused by the pollution of the optical path; the ultraviolet scanning multi-spectrum The measurement period of the water quality COD measuring instrument is only 3 minutes, which greatly improves the COD measurement speed; the correlation model between the ultraviolet characteristic spectrum and the COD of the water sample established by the BP neural network is more in line with the water sample with many pollutants and the absorbance and COD A real case where there is a non-linear relationship between values. Therefore, the scope of application of the instrument is expanded, and it can be suitable for online, fast and accurate analysis and testing of environmental water and various waste water COD.

Description of drawings

Fig. 1 is the circuit block diagram of the ultraviolet multi-spectrum online water quality COD fast measuring device of the present invention;

Fig. 2 is an embedded system circuit block diagram of the present invention;

Fig. 3 is a circuit block diagram of the single-chip microcomputer system of the present invention;

Fig. 4 is the structural representation of the ultraviolet spectroscopic scanning system of the present invention;

Fig. 5 is a schematic structural view of the automatic cleaning device of the present invention;

Fig. 6 is a software flowchart of the ultraviolet multi-spectral water quality COD detection device;

Fig. 7 is a schematic diagram of a BP neural network for establishing a correlation model between ultraviolet characteristic spectrum and water quality COD.

Detailed ways

An ultraviolet scanning multi-spectral water quality COD rapid detection method of the present invention: first, scan the water sample in the full ultraviolet band of 200nm to 400nm; secondly, calculate the absorption spectrum data of the full ultraviolet band according to the blank calibration results and scanning results, The third is to obtain multiple characteristic spectra reflecting the characteristics of organic pollution in water from all the absorbance data. The fourth is to use these characteristic spectra and corresponding COD values to establish a correlation model between the two using BP neural network. Fifth, , in the actual water sample measurement, the COD value of the water sample can be quickly retrieved by using the measured characteristic spectrum and the established correlation model.

As shown in Figure 1: a kind of ultraviolet scanning type multi-spectral water quality COD rapid detection device of the present invention is made up of flow measuring tank, solenoid valve and pipeline, automatic cleaning device, ultraviolet spectroscopic scanning system, single-chip computer system, Intel Strong ARM embedded It is composed of several parts such as microcomputer system. The dual-computer system composed of a single-chip microcomputer and an embedded microcomputer completes the scanning of the full-band UV of the water sample and the collection of the absorbance signals of each wavelength, and according to the spectral value calibrated by the blank, the 8 larger absorbance and The absorbance at 400nm and the sum of each absorbance are input into the BP neural network model that has been trained by similar water quality samples to calculate the COD data measured this time.

As shown in Figure 2, the embedded microcomputer system consists of a central processing circuit, storage circuit, RS232 serial interface, RS485 serial interface, Ethernet communication interface, LCD display interface, and touch screen interface. The touch screen interface is connected with the touch screen. The measurement data can be saved in the storage circuit and displayed on the LCD in the form of numerical values and curves. Short-range communication is performed through RS232 serial interface and RS485 serial interface, and remote Communication, use the touch screen to operate the menu of the detection device.

As shown in Figure 3, the single-chip microcomputer system is composed of an analog-to-digital conversion circuit, a pump valve control circuit, a stepper motor control drive circuit 1, a stepper motor control drive circuit 2, and a serial interface circuit, wherein the stepper motor control drive circuit 1 and The spectral scanning stepper motor is connected, and the stepper motor control drive circuit 2 is connected with the automatic cleaning device. The single-chip microcomputer system can regularly control the stepping motor of the planar grating spectroscopic system to scan the ultraviolet spectrum, and at the same time collect the scanning output signals of each wavelength through the analog-to-digital conversion circuit; according to the set cleaning time, control the automatic cleaning device to clean the optical window; The measured water sample enters the pump valve, controls the cleaning pump valve, and completes the functions of measurement and cleaning; the scanning spectrum data is transmitted to the embedded microcomputer system through the serial interface.

As shown in Figure 4: the ultraviolet multispectral scanning system is composed of a deuterium light source 1, a first converging lens 2, a second converging lens 4, a plane grating beam splitting system, and a silicon photodiode 11, wherein the plane grating beam splitting system is sequentially connected with the incident Slit 5, collimating objective lens 6, plane grating 8, condenser objective lens 7, plane grating 8, stepper motor 9, and exit slit 10 are connected. The light emitted by the deuterium lamp 1 passes through the converging lens 2 and becomes parallel light, enters the flow measurement tank 3 through the quartz glass window, and the light absorbed by the water sample enters the incident slit 5 through the converging lens 4, and is reflected by the collimating objective lens 6 After that, it becomes parallel light and enters the surface of the plane grating 8. The grating acts as a dispersive element to diffract and decompose the received composite light into spectra. After being converged by the focusing objective lens 7, it goes to the exit slit 10 to form a series of monochromatic slit images arranged by wavelength. . The movement of the stepper motor 9 is controlled by the single-chip microcomputer system 12 , and the absorbed light intensity of each wavelength with a resolution of 1 nm in the entire band from 200 nm to 400 nm can be scanned to obtain the absorbed light intensity into the silicon photodiode 11 . The photodiode converts the received light intensity signal into a corresponding electrical signal, so the light intensity signal of the full-band ultraviolet light absorbed by the measured water sample can be obtained, and then calculated according to the spectral value of pure water obtained during blank calibration Calculate the absorbance value for each wavelength.

The optical path of the planar grating splitting system adopts Czerney-Turne mode, the width of the entrance and exit slits is selected as 0.5mm, and the splitting device adopts a planar blazed grating of 1200g/mm. The focal length of the collimating objective lens and the focusing objective lens is 200nm, the relative aperture D/F=1/4.5, and the wavelength resolution is less than 0.5nm. Control the stepper motor to rotate forward and reverse to realize the scanning of the ultraviolet band, and the resolution of the scanning wavelength is 1nm.

As shown in Figure 5, automatic cleaning device is made of stepping motor 13, crankshaft linkage mechanism 14, cleaning rod 15, cleaning soft wipe 16. The single-chip microcomputer controls the cleaning stepper motor to work according to the set automatic cleaning time, and the crankshaft linkage mechanism converts the axial rotation of the stepper motor into the up and down movement of the cleaning rod, driving the double-sided cleaning soft wipe on the head of the cleaning rod and the circulation tank. Contact with the optical window to achieve the effect of cleaning the light-transmitting window.

Fig. 6 is a working flow chart of an ultraviolet scanning multi-spectrum water quality COD rapid detection device. After power on, initialize first, then turn on the pump and water inlet valve, so that the measured water sample enters the flow-through measurement tank; after the water flow is stable, control the optical system to scan in the ultraviolet band to obtain the ultraviolet absorption spectrum of the water sample, according to the blank calibrated Spectral value, calculate the absorbance of each wavelength; find out 8 larger absorbance values, 400nm absorbance and absorbance sum; then use the BP-LM fast algorithm of the neural network model to calculate the COD value of the water sample; finally The measurement data is displayed, alarmed, judged and saved. In addition to the main process, the program can respond to the operation of the buttons to realize functions such as blank calibration, data query, and setting of working parameters; and can perform automatic cleaning at regular intervals.

As shown in Figure 7: According to the multiple absorbance data obtained by ultraviolet scanning, the correlation model between spectral data and organic pollutant concentration (COD) is established by using BP artificial neural network, and the extrapolation ability of the model is obtained by the tested water The COD data of the water sample can be deduced from the multiple UV absorbance data of the sample. The BP artificial neural network layer structure established by this system is 10-20-1. The input layer consists of 10 nodes, respectively input 8 large absorbance data obtained in the ultraviolet band, the 9th is the absorbance data of visible light with a wavelength of 400nm (as a reference signal of influencing factors such as light source and particles), and the 10th is the sum of absorbance. The hidden layer uses 20 nodes, and the output layer is 1 node, which is the COD data obtained through the calculation of the artificial neural network.

Claims (6)

1, a kind of ultraviolet scanning type multi-spectral water quality COD rapid detection method is characterized in that, it comprises the steps: 1) First, scan the water sample in the full range of ultraviolet light from 200nm to 400nm; 2) According to the blank calibration results and scanning results, calculate the absorption spectrum data of the whole ultraviolet band; 3) Obtain multiple characteristic spectra reflecting the organic pollution characteristics of the water body from all the absorbance data; 4) Using these characteristic spectra and corresponding COD values, use BP neural network to establish a correlation model between the two; 5) In the actual water sample measurement, use the measured characteristic spectrum and the established correlation model to quickly invert the COD value of the water sample. 2, a kind of ultraviolet scanning type multi-spectrum water quality COD rapid detection device utilizing method as claimed in claim 1, it is characterized in that, embedded microcomputer system is connected to single-chip microcomputer system, and single-chip microcomputer system is connected to spectral scanning stepping motor, measuring valve successively , the cleaning valve, and the flow measuring tank are respectively connected with the automatic cleaning device, the water sample outlet, the cleaning valve, and the measuring valve. The cleaning valve is connected with the cleaning water inlet, and the measuring valve is connected with the measured water sample inlet. After the ultraviolet light is converged, it passes through the measuring tank. After being absorbed by the water sample, the ultraviolet light is concentrated and incident on the plane grating spectroscopic system. After the light is split, it is incident on the photoelectric conversion circuit. 3. A UV-scanning multi-spectral water quality COD rapid detection device according to claim 2, characterized in that, the circuit of the embedded microcomputer system is: the central processing circuit is connected with the RS232 serial interface circuit and the RS485 serial interface circuit respectively. Row interface circuit, touch screen interface circuit, storage circuit, Ethernet communication interface circuit, and LCD display interface circuit are connected, wherein the LCD display interface is connected with the 5.7" TFT display screen, and the touch screen interface is connected with the touch screen. 4. An ultraviolet scanning multi-spectral water quality COD rapid detection device according to claim 2, characterized in that the circuit of the single-chip microcomputer system is: a single-chip microcomputer circuit and an analog-to-digital conversion circuit, a pump valve control circuit, a stepper The motor control driving circuit 1, the stepping motor control driving circuit 2, and the serial interface circuit are connected, the stepping motor control driving circuit 1 is connected with the spectral scanning stepping motor, and the stepping motor control driving circuit 2 is connected with the automatic cleaning device . 5. An ultraviolet scanning multi-spectral water quality COD rapid detection device according to claim 2, wherein the ultraviolet multi-spectral scanning system consists of a deuterium light source 1, a first converging lens 2, and a second converging lens 4. The planar grating light splitting system and silicon photodiode 11 are composed, wherein the planar grating light splitting system is sequentially connected with the incident slit 5, the collimating objective lens 6, the planar grating 8, the condenser objective lens 7, the planar grating 8, the stepper motor 9, the exit slit Seam 10 connected. 6. An ultraviolet scanning multi-spectral water quality COD rapid detection device according to claim 4, characterized in that the automatic cleaning device consists of a stepping motor 13, a crankshaft linkage mechanism 14, a cleaning rod 15, a cleaning soft Rub 16 composition.

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