Method and device for detecting BOD (Biochemical Oxygen Demand) in water quality by ultraviolet induced fluorescence based on secondary diffraction calibration

Abstract

The invention belongs to the technical field of water quality detection, and discloses an ultraviolet-induced fluorescence water quality BOD (Biochemical Oxygen Demand) detection method and device based on secondary diffraction calibration. A pulse signal output by the control unit triggers the power supply module to drive the excitation light source, pulse excitation light generated by the light source is collimated by the collimating lens to form a collimated emission light beam, the collimated emission light beam is sent to the emission optical filter, excitation light of the light source is emitted through the emission optical filter, and interference light in the excitation light is filtered out; the excitation light excites the detected water body to generate a fluorescence signal, the fluorescence signal is emitted to the spectrum detection unit, the signal processing unit carries out real-time processing and analysis on spectrum data of the fluorescence signal, and real-time measurement of the BOD concentration of the water body is completed through an established BOD quantitative analysis model. By monitoring the intensity of secondary diffraction light in a water body spectrum curve, the BOD fluorescence peak intensity is compensated, and non-contact, real-time and rapid measurement of water quality BOD parameters is realized.

Description

Technical Field

[0001] This invention belongs to the field of water quality testing technology, and particularly relates to a method and apparatus for detecting BOD in water quality based on second-order diffraction calibration using ultraviolet-induced fluorescence. Background Technology

[0002] Water quality monitoring provides an accurate, comprehensive, and timely reflection of water environment quality and pollution status, and is a key aspect of modern environmental management. Biochemical oxygen demand (BOD) is a crucial parameter characterizing the amount of biodegradable organic matter in water. It is defined as the amount of oxygen required by aerobic microorganisms to decompose biodegradable organic matter in a given water body within a specific time period (usually 5 days) at 20°C, expressed in mg / L. Generally, a higher BOD value indicates a higher risk of pollutants being degraded by microorganisms in the water's own environment, leading to a sharp decrease in dissolved oxygen and causing a series of ecological problems. Traditional BOD detection uses the five-day incubation method, which involves culturing the water body under closed, constant-temperature conditions for five days. The inherent microbial population in the water body is used to biochemically degrade biodegradable pollutants, and the difference in dissolved oxygen content before and after incubation is calculated; the result is called five-day biochemical oxygen demand (BOD5). Traditional methods of measurement have several limitations: long detection cycles, complex analytical procedures, low reproducibility, and susceptibility to numerous interfering factors. Furthermore, the equipment used in these methods is bulky, expensive, and poorly portable, hindering real-time and rapid water quality monitoring and making it impossible to provide timely and effective early warnings of sudden water pollution events. Adopting real-time monitoring technology to rapidly estimate BOD values ​​would significantly enhance the ability of environmental managers and regulators to predict the degree of organic pollution in water bodies, enabling them to take timely and effective countermeasures and thus address environmental pollution problems more quickly and accurately.

[0003] Fluorescence spectroscopy, due to its high sensitivity and selectivity, has become a highly promising method for spectroscopic water quality detection. This technology utilizes the close correlation between microbial activity and BOD5 and bacterial contamination in wastewater, achieving quantitative analysis of BOD values ​​by detecting the fluorescence intensity of tryptophan under ultraviolet light excitation. Currently, three-dimensional fluorescence spectroscopy is the primary method for BOD detection in water. In 2008, Naomi Hudson first systematically studied the correlation between the three-dimensional fluorescence spectral characteristics of various fluorescent substances in water and BOD5, finding a significant linear relationship between BOD5 concentration and the intensity of the tryptophan T1 fluorescence peak (correlation coefficient r>0.9), laying the theoretical foundation for estimating BOD using tryptophan concentration. Subsequently, Henderson et al. (2009) also confirmed the strong correlation between the tryptophan T1 fluorescence peak and BOD5 in a review of fluorescence water quality monitoring. In 2013, Bridgeman et al. further discovered a high correlation (r=0.92) between the T1 peak intensity of an unfiltered sample during wastewater treatment and BOD, providing a new approach for real-time monitoring and process control of wastewater quality.

[0004] While three-dimensional fluorescence spectroscopy has achieved some success in detecting BOD in water, it still suffers from limitations such as large equipment size, complex data processing, and difficulty in achieving real-time online detection. In contrast, two-dimensional fluorescence spectroscopy uses a single-wavelength LED or laser as the excitation source, simplifying the measurement device and significantly improving detection efficiency by only requiring analysis of two-dimensional spectral curves. In recent years, this technology has shown promising application prospects in water quality detection. However, during the detection process, changes in excitation light output power and external environmental factors can affect fluorescence intensity to some extent, interfering with the measurement results. To ensure the stability of the measurement results, there are currently two main solutions: the first is to monitor the output power of the excitation light and compensate for changes in excitation light output power to achieve stability of the measurement results; the second method is to monitor the Raman peak intensity of the water and compensate for changes in Raman peak intensity to achieve stability of the measurement results. Summary of the Invention

[0005] To overcome the problems existing in related technologies, the present invention discloses an embodiment of a method and apparatus for detecting BOD in water quality based on second-order diffraction calibration using ultraviolet-induced fluorescence.

[0006] The technical solution is as follows: A UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration, the device includes a light source; the pulsed excitation light generated by the light source is collimated by a collimating lens to form a collimated emission beam, and sent to an emission filter, through which the excitation light of the light source is emitted and the interference light in the excitation light is filtered out; The emitted excitation light induces fluorescence in the water body, which is then transmitted to a spectral detection unit. The spectral detection unit processes the fluorescence signal to obtain an electrical signal, which is then sent to a signal processing unit for further processing to obtain a spectral curve.

[0007] The signal processing unit processes and analyzes the spectral data of the fluorescence signal in real time, establishes a quantitative BOD analysis model, and completes the real-time measurement of BOD concentration in the water.

[0008] The quantitative analysis model for BOD is the correlation between the BOD value of a BOD standard solution and its corresponding ratio of spectral fluorescence to second-order diffraction intensity.

[0009] Furthermore, the pulse signal output by the control unit triggers the power supply module to drive the excitation light source to generate pulsed excitation light output, which is then sent to the collimating lens for collimation.

[0010] The spectral detection unit is used to receive the fluorescence signal generated by the water body induced by the excitation light emitted by the emission filter, and is composed of a spectrometer, a coupling optical fiber, a focusing lens, and a receiving filter in sequence. The fluorescence signal is sent to the receiving filter, which receives the fluorescence signal generated by the water body induced by the excitation light and sends it to the focusing lens. The focusing lens focuses and couples the signal to the coupling optical fiber and inputs it to the spectrometer.

[0011] The signal processing unit uses a microcontroller, Raspberry Pi, or microcomputer to process and analyze spectral data in real time and output BOD measurement parameters.

[0012] The control unit synchronously triggers the spectrometer of the spectral detection unit to collect fluorescence signals generated by the water body in real time and inputs them into the signal processing unit.

[0013] Another objective of this invention is to provide a UV-induced fluorescence method for detecting BOD in water quality based on second-order diffraction calibration, comprising: The pulse signal output by the control unit triggers the power supply module, which drives the excitation light source to generate pulse excitation light output. After being collimated by the collimating lens and passing through the emission filter, the light is incident on the water body being measured. When water is stimulated, it generates a fluorescence signal. This fluorescence signal, induced by the excitation light, is received by a receiving filter and focused by a focusing lens, coupled to a coupling fiber, and input into a spectrometer. Simultaneously, the control unit triggers the spectrometer to acquire the fluorescence signal generated by the water in real time. The spectrometer processes the fluorescence signal to obtain an electrical signal, which is then input into a signal processing unit. The signal processing unit processes and analyzes the electrical signal to obtain spectral data. The signal processing unit uses an established second-order diffraction light signal calibration reference light formula to compensate for the changing excitation light intensity output by the light source and the measurement error of BOD concentration fluorescence caused by changes in the water environment, thus completing the real-time measurement of BOD concentration in the water.

[0014] Fluorescence signals generated by water stimulation include excitation light signals. Second-order diffraction light signal Fluorescence background signal at the wavelength of the second-order diffraction light signal BOD characteristic fluorescence signal and organic fluorescence signals BOD fluorescence intensity is linearly related to BOD concentration. (1); In the formula, This is the proportionality coefficient. The detection limit; The established formula for the calibration reference light of the second-order diffraction signal is as follows: (2); In the formula, The relative fluorescence intensity is... This is the proportionality coefficient. This is the detection limit.

[0015] The application of the UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration in real-time water quality early warning and water pollution detection.

[0016] The UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration is applied to the quantitative analysis of BOD value by measuring the fluorescence intensity generated by tryptophan under UV light excitation.

[0017] Combining all the above technical solutions, the beneficial effects of this invention are as follows: This invention achieves non-contact, real-time, and rapid measurement of water quality BOD parameters by monitoring the intensity of second-order diffraction light and the intensity of BOD fluorescence peaks in the water body's spectral curve. This technology can be widely applied to online BOD monitoring of various water bodies such as rivers, lakes, and oceans. By timely capturing information on changes in water quality BOD, it can quickly respond to sudden pollution events, thereby effectively reducing the impact of pollutants on the aquatic ecological environment and maintaining the protection and sustainable development of aquatic ecosystems. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure; Figure 1 This is a schematic diagram of the UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of spectral overlap provided in an embodiment of the present invention; Figure 3This is a schematic diagram of a typical spectral curve generated by water body excitation according to an embodiment of the present invention; Figure 4 This is a spectral curve of BOD standard solutions of different concentrations provided by the present invention; Figure 5 This is a graph showing the correlation between the BOD value and fluorescence intensity of the standard solution provided by this invention. In the diagram: 1. Light source; 2. Control unit; 3. Collimating lens; 4. Signal processing unit; 5. Emitting filter; 6. Spectrometer; 7. Coupler fiber; 8. Focusing lens; 9. Receiving filter; 10. Power supply module. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] The innovation of this invention lies in its ability to achieve non-contact, real-time online measurement of BOD parameters in water. The device uses a specific wavelength of ultraviolet light to excite the water, generating spectral signals of fluorescence and second-order diffraction. In experiments, based on standard solution calibration, a quantitative relationship model between BOD concentration and the ratio of fluorescence-second-order diffraction spectral characteristics was established, thereby enabling rapid detection of BOD in actual water bodies.

[0021] Example 1, such as Figure 1 As shown, the ultraviolet-induced fluorescence water quality BOD detection device (small water quality BOD detection system) based on second-order diffraction calibration provided in this embodiment of the invention consists of a light source 1 (excitation light source), a control unit 2, a spectral detection unit, and a signal processing unit 4.

[0022] The light source 1 uses a laser or LED, which forms a collimated emission beam through the collimating lens 3 and sends it to the emission filter 5. The emission filter 5 is a bandpass filter that allows the excitation light emitted from the light source 1 to pass through and filters out other interfering light (interfering light in the excitation light other than the excitation wavelength) within the excitation light. The emitted excitation light induces fluorescence in the water, which is then transmitted to a spectral detection unit. This unit processes the fluorescence signal to obtain an electrical signal – a common technique in this field. The light signal enters the spectrometer 6 through an entrance slit. After passing through a dispersive element, the light is separated into a continuous monochromatic band from ultraviolet to infrared. The separated monochromatic light falls onto a photodetector (such as a CCD or photodiode), converting the light signal into an electrical signal. The electrical signal output from the spectral detection unit is sent to a signal processing unit 4 for processing to obtain a spectral curve. After amplification and analog-to-digital conversion, the electrical signal is processed by a computer to generate an intensity-wavelength spectrum.

[0023] Signal processing unit 4 performs real-time processing and analysis of the spectral data of fluorescence signals, and completes real-time measurement of BOD concentration in water by establishing a quantitative BOD analysis model. The quantitative analysis model for BOD is the correlation between the BOD value of a BOD standard solution and its corresponding ratio of spectral fluorescence to second-order diffraction intensity.

[0024] For example, the spectral detection unit is used to receive the fluorescence signal generated by the water body induced by the excitation light emitted by the emission filter 5, and is composed of a spectrometer 6, a coupling fiber 7, a focusing lens 8, and a receiving filter 9 in sequence; the fluorescence signal is sent to the receiving filter 9, the receiving filter 9 receives the fluorescence signal generated by the water body induced by the excitation light and sends it to the focusing lens 8, the focusing lens 8 focuses and couples it to the coupling fiber 7 and inputs it to the spectrometer 6.

[0025] For example, the signal processing unit 4 can be a microcontroller, Raspberry Pi, or microcomputer, responsible for real-time processing and analysis of spectral data and outputting BOD measurement parameters.

[0026] The pulse signal output by the control unit 2 triggers the power supply module 10 to drive the excitation light source 1 to generate pulse excitation light output, which is sent to the collimating lens 3 for collimation.

[0027] An exemplary working principle of the UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration: First, the pulse signal output by the control unit 2 triggers the power supply module 10 to drive the excitation light source 1 to generate pulsed excitation light output. After being collimated by the collimating lens 3 and passing through the emission filter 5, the light is incident on the water body to be measured. The water body is excited and generates a fluorescence signal. The fluorescence signal induced by the excitation light from the receiving filter 9 is focused and coupled to the coupling fiber 7 by the focusing lens 8 and input into the spectrometer 6.

[0028] Simultaneously, the control unit 2 triggers the spectrometer 6 to collect the fluorescence spectrum signal generated by the water body in real time, and inputs it into the signal processing unit 4 to process the spectral data. Through the established BOD quantitative analysis model, the real-time rapid measurement of the BOD concentration in the water body is realized.

[0029] As demonstrated by the above embodiments, this invention proposes an ultraviolet-induced fluorescence water quality BOD detection device based on second-order diffraction calibration. This device enables real-time monitoring of BOD parameters in various water bodies, including rivers, lakes, and oceans, providing timely information on water pollution status. The widespread application of this technology will effectively improve water quality monitoring efficiency, contribute to environmental pollution prevention and control and ecological protection, and is of great significance for promoting a green economy and sustainable development. In the future, by deeply exploring market demand, a series of detection devices can be developed for different application scenarios (such as industrial wastewater, municipal sewage, and natural water bodies). Leveraging its technological advantages, the invention can gradually expand into the international market, offering broad market prospects and significant economic benefits.

[0030] Existing methods for detecting BOD in water, such as the five-day culture method, microbial sensor method, pressure measurement method, microbial electrode method, activated sludge aeration degradation method, and reduced-pressure coulometric method, have limitations due to their long detection times, making them unsuitable for the current urgent need for rapid water quality testing. This invention proposes a rapid BOD measurement device that achieves rapid detection of BOD parameters based on the intensity ratio of the fluorescence signal generated after water excitation to the second-order diffraction light signal. This method can be widely applied to real-time monitoring of various water bodies, providing timely and effective feedback on water pollution status.

[0031] This invention enables real-time and rapid measurement of water quality BOD parameters.

[0032] Example 2, the UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration provided in this embodiment of the invention includes: The pulse signal output by the control unit 2 triggers the power supply module 10 to drive the excitation light source 1 to generate pulse excitation light output. After being collimated by the collimating lens 3 and passing through the emission filter 5, the light is incident on the water body to be measured. When water is stimulated, it generates a fluorescence signal. This signal is received by the receiving filter 9 and focused by the focusing lens 8, coupled to the coupling fiber 7, and input to the spectrometer 6. Simultaneously, the control unit 2 triggers the spectrometer 6 to acquire the fluorescence signal generated by the water in real time. The spectrometer 6 processes the fluorescence signal to obtain an electrical signal, which is then input to the signal processing unit 4. The signal processing unit 4 processes and analyzes the electrical signal to obtain spectral data. The signal processing unit 4 uses an established second-order diffraction light signal calibration reference light formula to compensate for the changing excitation light intensity output by the light source 1 and the measurement error of BOD concentration fluorescence in the water caused by changes in the water environment, thus completing the real-time measurement of BOD concentration. By performing spectral detection on a standard solution with a known BOD concentration, spectral curves corresponding to different concentrations are obtained, and the ratio of fluorescence intensity to second-order diffraction light intensity is calculated. Based on the correspondence between this ratio and the BOD concentration value, a quantitative analysis model for BOD is established. In actual testing, the BOD concentration of the water sample can be quickly calculated by measuring the spectral curve of the water sample and calculating the corresponding light intensity ratio, and then substituting it into the established model.

[0033] For example, the spectrometer 6 used in this invention is a grating-based spectrometer. Due to the order characteristics of grating diffraction, the first-order diffracted light (m=1) and the second-order diffracted light (m=2) may overlap at a specific wavelength position, such as... Figure 2 As shown in the spectral overlap diagram, the spectral peak of short-wavelength (such as ultraviolet light) incident light will appear at twice the wavelength of spectrometer 6. In the measured water spectral curve, a second-order diffraction characteristic peak located at twice the excitation light wavelength can be observed.

[0034] Figure 3 The typical spectral curve generated by water excitation mainly includes the excitation light signal. Second-order diffraction light signal Fluorescence background signal at the wavelength of the second-order diffraction light signal BOD characteristic fluorescence signal and organic fluorescence signals ( Figure 3 The horizontal axis represents the emitted light wavelength, and the vertical axis represents the emitted light intensity. Generally, as the BOD concentration in water increases, the corresponding fluorescence signal intensity also increases; therefore, the BOD fluorescence intensity can be considered to have a linear relationship with its concentration. (1); In the formula, This is the proportionality coefficient. Both the detection limit and the reference light source are constants that can be determined experimentally. However, in actual detection processes, the instability of the output power of light source 1 and changes in the aquatic environment can interfere with the fluorescence measurement results. Therefore, to eliminate these systematic errors and improve the reliability of the detection results, this invention innovatively proposes the following formula for the calibration reference light of the second-order diffraction signal: (2); In the formula, The relative fluorescence intensity is... This is the proportionality coefficient. As the detection limit, the influence of changes in excitation light intensity and environmental changes on BOD parameter measurement can be greatly eliminated by formula (2).

[0035] To further illustrate the effects of the embodiments of the present invention, the following experiments were conducted: During the experimental measurement, the present invention used a microcomputer as the signal processing unit 4, a 265nm ultraviolet LED as the excitation light source 1, and a spectrometer 6 with a measurement range of 300-850nm for spectral measurement. The optical probe of the detection system was maintained at a fixed distance of 20-30cm from the water surface. To ensure the reliability and stability of the detection results, the present invention sets the emission of the pulsed light source and the signal reception of the spectrometer 6 to be synchronized, which can minimize environmental interference.

[0036] Based on the aforementioned instrument parameters, this invention employs a self-developed UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration to systematically detect BOD standard solution gradient samples within the concentration range of 0-10 mg / L. Through spectral acquisition and data processing, the relative fluorescence intensity of solutions at different BOD concentrations was obtained, and a quantitative relationship model between BOD concentration and fluorescence intensity was established. This model can be applied to the measurement of BOD parameters in actual water quality. Experimental results are as follows: Figure 4 , Figure 5 As shown. Figure 4 The spectral curves of BOD standard solutions at different concentrations are shown, representing the spectral curves of standard solutions with BOD concentrations of 0, 2, 4, 6, 8, and 10 mg / L. Since the spectral range is 300-850 nm, the peak of the 265 nm excitation source is not visible on the spectral curves measured by spectrometer 6, but a second-order diffraction peak at 530 nm is clearly observed. It can be seen that with increasing BOD concentration, the intensity of the characteristic fluorescence signal of BOD at 320 nm shows a regular increase. Figure 5 The correlation between BOD value and fluorescence intensity of standard solutions was analyzed, showing the relationship between BOD concentration and spectral fluorescence intensity in the range of 0-10 mg / L. The horizontal axis represents BOD concentration, and the vertical axis represents the corresponding fluorescence intensity. Figure 5As can be seen, within this concentration range, fluorescence intensity is significantly positively correlated with BOD concentration (r² = 0.971), and its linear regression equation is shown as the red fitted line, with the expression being: (3); In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration, characterized in that, The device includes a light source (1); the pulsed excitation light generated by the light source (1) is collimated by the collimating lens (3) to form a collimated emission beam, and sent to the emission filter (5). The excitation light of the light source (1) is emitted through the emission filter (5), and the interference light in the excitation light is filtered out. The emitted excitation light induces the water body to generate a fluorescence signal, which is then emitted to the spectral detection unit. The spectral detection unit processes the fluorescence signal to obtain an electrical signal. The electrical signal output by the spectral detection unit is sent to the signal processing unit (4) for processing to obtain a spectral curve. The signal processing unit (4) processes and analyzes the spectral data of the fluorescence signal in real time. By establishing a quantitative BOD analysis model, the real-time measurement of the BOD concentration in the water body is completed. The quantitative analysis model for BOD is the correlation between the BOD value of a BOD standard solution and its corresponding ratio of spectral fluorescence to second-order diffraction intensity.

2. The UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration according to claim 1, characterized in that, The pulse signal output by the control unit (2) triggers the power supply module (10) to drive the excitation light source (1) to generate pulse excitation light output, which is sent to the collimating lens (3) for collimation.

3. The UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration according to claim 1, characterized in that, The spectral detection unit is used to receive the fluorescence signal generated by the water body induced by the excitation light emitted by the emission filter (5), and is composed of a spectrometer (6), a coupling fiber (7), a focusing lens (8), and a receiving filter (9) in sequence. The fluorescence signal is sent to the receiving filter (9), which receives the fluorescence signal generated by the water body induced by the excitation light and sends it to the focusing lens (8). The focusing lens (8) focuses and couples the signal to the coupling fiber (7) and inputs it into the spectrometer (6).

4. The UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration according to claim 1, characterized in that, The signal processing unit (4) is a microcontroller, Raspberry Pi or microcomputer, responsible for real-time processing and analysis of spectral data and outputting BOD measurement parameters.

5. The UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration according to claim 2, characterized in that, The control unit (2) synchronously triggers the spectrometer (6) of the spectral detection unit to collect the fluorescence spectral signal generated by the water body in real time and input it into the signal processing unit (4).

6. A UV-induced fluorescence method for detecting BOD in water quality based on second-order diffraction calibration, characterized in that, The method implemented in any one of claims 1-5, using the UV-induced fluorescence water quality BOD detection device based on second-order diffraction calibration, comprises: The pulse signal output by the control unit (2) triggers the power supply module (10) to drive the excitation light source (1) to generate pulse excitation light output. After being collimated by the collimating lens (3) and passing through the emission filter (5), it is incident on the water body to be measured. The water body generates a fluorescence signal when stimulated. The fluorescence signal induced by the excitation light is received by the receiving filter (9). The fluorescence signal is focused and coupled to the coupling fiber (7) through the focusing lens (8) and input into the spectrometer (6). At the same time, the control unit (2) synchronously triggers the spectrometer (6) to collect the fluorescence signal generated by the water body in real time. The spectrometer (6) processes the fluorescence signal to obtain an electrical signal and inputs it into the signal processing unit (4). The signal processing unit (4) processes and analyzes the electrical signal to obtain spectral data. The signal processing unit (4) compensates for the changing excitation light intensity output by the light source (1) and the measurement error of the BOD concentration fluorescence formed by the changing water environment by establishing the second-order diffraction light signal calibration reference light formula, and completes the real-time measurement of the BOD concentration of the water body.

7. The UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration according to claim 6, characterized in that, Fluorescence signals generated by water stimulation include excitation light signals. Second-order diffraction light signal Fluorescence background signal at the wavelength of the second-order diffraction light signal BOD characteristic fluorescence signal and organic fluorescence signals BOD fluorescence intensity is linearly related to BOD concentration. （1）； In the formula, This is the proportionality coefficient. The detection limit; The established formula for the calibration reference light of the second-order diffraction signal is as follows: （2）； In the formula, The relative fluorescence intensity is... This is the proportionality coefficient. This is the detection limit.

8. The UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration according to claim 6, characterized in that, The application of the UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration in real-time water quality early warning and water pollution detection.

9. The UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration according to claim 6, characterized in that, The UV-induced fluorescence water quality BOD detection method based on second-order diffraction calibration is applied to the quantitative analysis of BOD value by measuring the fluorescence intensity generated by tryptophan under UV light excitation.

Images