UV-method COD (Chemical Oxygen Demand) detection method and system with turbidity compensation

Abstract

The invention relates to a UV-method COD detection method and system with turbidity compensation, and belongs to the technical field of water quality detection.The UV-method COD detection method comprises the following steps that S100, at least two COD standard solutions with different concentrations are obtained and marked as a standard solution S1, a standard solution S2 and a standard solution SN, and the absorbance of the standard solution S1, the absorbance of the standard solution S2 and the absorbance of the standard solution SN are measured respectively; s200, establishing an initial equation of the COD concentration and the absorbance based on the COD concentration and the absorbance of the COD standard liquid with different concentrations; s300, performing calibration adjustment on the initial equation to obtain a calibration equation; and S400, substituting the calibration equation as an initial equation, obtaining the COD standard liquid again, and repeating the step S300. The method has the effect of reducing the COD concentration detection calculation amount.

Description

Technical Field

[0001] The present application relates to the technical field of water quality detection, and in particular to a UV COD detection method and system with turbidity compensation. Background Art

[0002] COD (Chemical Oxygen Demand) refers to the oxidation of organic matter and reducing substances in a water sample by a strong oxidant (such as potassium dichromate or potassium permanganate) under certain conditions. Its value is expressed in milligrams of oxygen consumed per liter of water sample (mg / L). COD is an important indicator of the degree of organic pollution in water bodies. The higher the value, the more serious the pollution.

[0003] Existing technologies primarily use UV methods to measure COD concentration. UV methods determine concentration based on a substance's absorption of ultraviolet light. However, in practice, water sample turbidity can interfere with measurement results. Turbidity is primarily caused by suspended matter, colloids, and dissolved organic matter in the water, which also absorb ultraviolet light, leading to inflated COD values.

[0004] To address this issue, existing UV-based COD concentration measurement technologies mostly employ computationally intensive methods such as AI (artificial intelligence), concentration learning, and linear fitting, combined with spectral analysis. While these methods improve measurement accuracy, their complex algorithms and high computational effort make them difficult to implement in single-chip microcomputers. Consequently, they cannot be implemented as small sensor-like devices, limiting their application in areas such as rapid on-site testing and online monitoring. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems and to reduce the interference of turbidity on the detection results when the UV method is used to measure COD concentration on a single chip, the present application provides a UV method COD detection method and system with turbidity compensation.

[0006] In the first aspect, the present application provides a UV COD detection method with turbidity compensation, which adopts the following technical solution:

[0007] A UV COD detection method with turbidity compensation comprises the following steps:

[0008] S100, obtaining at least two COD standard solutions of different concentrations, denoted as standard solution S1, standard solution S2, and standard solution SN, and measuring the absorbance of the standard solution S1, the standard solution S2, and the standard solution SN, respectively;

[0009] S200, establishing an initial equation of COD concentration and absorbance based on the COD concentration and absorbance of the COD standard solutions of different concentrations;

[0010] S300, calibrating and adjusting the initial equation to obtain a calibration equation;

[0011] S400: Substitute the calibration equation as the initial equation, re-obtain the COD standard solution, and repeat step S300.

[0012] Preferably, based on the COD concentration and absorbance of the COD standard solutions of different concentrations, an initial equation of COD concentration and absorbance is established, comprising the following steps:

[0013] Substituting the obtained COD concentration and absorbance of the standard solution into the general formula Y=K*X+B respectively to obtain at least two sets of equations, wherein Y is the COD concentration, X is the absorbance, and K and B are both constants;

[0014] The specific values ​​of K and B were solved through the equation system and substituted into the general formula to obtain the initial equation of COD concentration and absorbance.

[0015] Preferably, the calibration adjustment of the initial equation to obtain a calibration equation comprises the following steps:

[0016] Prepare two calibration solutions with different COD concentrations, record them as calibration solution T1 and calibration solution T2, and calculate the absorbance of the calibration solution T1 after deducting the effect of turbidity and the absorbance of the calibration solution T2 after deducting the effect of turbidity respectively;

[0017] Based on the COD concentrations of the calibration solutions T1 and T2 and the absorbance after deducting the influence of turbidity, the initial equation of COD concentration and absorbance is adjusted to obtain a calibration equation of COD concentration and absorbance by calculation.

[0018] Preferably, calculating the absorbance of the calibration solution T1 after deducting the effect of turbidity and the absorbance of the calibration solution S2 after deducting the effect of turbidity comprises:

[0019] Obtaining the incident light intensity and the transmitted light intensity of the calibration solution under ultraviolet light irradiation, and the incident light intensity and the transmitted light intensity of the calibration solution under visible light irradiation;

[0020] Based on the incident light intensity and transmitted light intensity obtained, the absorbance of the calibration solution under ultraviolet light and the absorbance under visible light are calculated respectively, and the absorbance of the calibration solution after deducting the influence of turbidity can be obtained by subtracting the two.

[0021] Preferably, based on the COD concentrations of the calibration solution T1 and the calibration solution 2 and the absorbance after deducting the influence of turbidity, adjusting the initial equation of COD concentration and absorbance, and calculating the calibration equation of COD concentration and absorbance, comprises the following steps:

[0022] Zero calibration: Substitute the COD concentration C3 of the calibration solution T1 and the absorbance A3 after deducting the influence of turbidity into the initial equation and correct the constant B by calculation;

[0023] Slope calibration: Substitute the COD concentration C4 and absorbance A4 of the calibration solution T2, as well as the COD concentration C3 and absorbance A3 after deducting the influence of turbidity of the calibration solution T1 into the equation after zero calibration, and correct the constant K by calculation.

[0024] Preferably, the COD concentration C3 of the calibration solution T1 is close to 0 mg / L; and the COD concentration C4 of the calibration solution T2 is much greater than C3.

[0025] Preferably, in two adjacent calibration adjustment processes, the turbidity concentration ratio of the calibration solution is inconsistent.

[0026] In a second aspect, a UV COD detection system with turbidity compensation according to the first aspect is provided, wherein the UV COD detection system comprises a detection device and a display device;

[0027] The detection device is used to measure the COD concentration of the liquid and output the detection result;

[0028] The display device is used to receive and display the detection result of the detection device.

[0029] Preferably, the detection device comprises:

[0030] Optical path module: equipped with an emitting light source of at least two wavelengths and a light intensity receiving group corresponding to the emitting light source; the emitting light source is used to emit detection light of the required wavelength; the light intensity receiving group is used to obtain the light intensity information of the detection light;

[0031] Main control module: used to output a digital control signal to control the emission light source to emit detection light intensity, and receive the light intensity information measured by the light intensity receiving group, and calculate the COD concentration based on the light intensity information;

[0032] Signal processing module: used to receive the digital control signal output by the main control module and convert the digital control signal into an analog control signal and output it to the optical path module, and at the same time convert the light intensity information collected by the light intensity receiving group into a voltage signal and output it to the main control module;

[0033] Data transmission module: used to transmit the detection results calculated by the main control module.

[0034] Preferably, the optical path module further comprises a filter, which is arranged at the output end of the emitting light source and is used to filter light;

[0035] The light intensity receiving group includes two receivers, one of which is used to measure the incident light intensity of the detection light, and the other is used to measure the transmitted light intensity.

[0036] In summary, this application includes at least one of the following beneficial technical effects:

[0037] 1. Through the calculation of turbidity compensation, when detecting the COD concentration of the liquid to be tested, the dual-wavelength detection light is alternately irradiated on the liquid to be tested, effectively eliminating the interference of turbidity on COD concentration measurement and improving the accuracy of COD concentration measurement;

[0038] 2. Reduce the amount of calculation required for calculating the COD concentration of the liquid to be tested. By calibrating and adjusting the general equation to obtain a calibration equation, the detection system can quickly calculate the COD concentration of the liquid to be tested when the absorbance of the liquid to be tested is detected by calling the calibration equation. This avoids the use of high-computation methods such as AI learning, concentration learning, and online fitting, and reduces the complexity of the algorithm, so that the detection device can be implemented in a single-chip microcomputer.

[0039] 3. Due to the small amount of calculation, the detection device can be implemented in a single-chip microcomputer, so that the present application solution can be applied to small sensor-type devices, facilitating the realization of on-site rapid detection and online monitoring functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the overall process of the UV COD detection method in the embodiment of the present application;

[0041] Figure 2 This is a partial flow diagram of the UV COD detection method in the embodiment of the present application;

[0042] Figure 3 It is a modular schematic diagram of the UV COD detection system in the embodiment of the present application.

[0043] Explanation of the accompanying drawings: 1. Detection device; 11. Optical path module; 111. Transmitting light source; 112. Light intensity receiving group; 12. Main control module; 13. Signal processing module; 14. Data transmission module; 2. Display device. DETAILED DESCRIPTION

[0044] The following will further describe in detail the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the embodiments described in this solution are only part of the embodiments of the present application, not all of the embodiments.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0046] COD is a core indicator for assessing the degree of organic pollution in water. Turbidity is primarily caused by suspended particles in the water, such as soil, sand, organic matter, inorganic matter, plankton, and microorganisms. The size, shape, and refractive index of these particles affect the intensity of light scattering. Therefore, turbidity is related not only to the suspended matter content but also to its physical properties. For example, small particles of the same mass scatter light more easily than larger particles, resulting in higher turbidity values.

[0047] The relationship between COD and turbidity. When using the UV method to detect the COD concentration in water, it is easily affected by particles such as soil, sand, organic matter, inorganic matter, plankton, and microorganisms suspended in the water. That is, turbidity has a certain interference on the accuracy of COD measurement and detection.

[0048] When light propagates through a solution, the medium absorbs it, causing the light intensity in the original propagation direction to attenuate. Therefore, by detecting the degree of light intensity attenuation, it is possible to quantitatively analyze the substances in the solution. The absorbance, or degree of absorption of a light source of a certain wavelength by dissolved organic matter in water, can be measured and converted into COD concentration. Absorbance is a physical quantity that describes the degree to which light is absorbed when passing through a substance. It is defined as the logarithm of the ratio of incident light intensity to transmitted light intensity. Absorbance can be used to measure light intensity and calculate other parameters.

[0049] Since COD components mainly absorb ultraviolet light and do not absorb visible light, while turbidity components can absorb both ultraviolet light and visible light, based on this characteristic, the present application discloses a UV COD detection method with turbidity compensation. Figures 1 to 2 , a UV COD detection method with turbidity compensation includes:

[0050] S100. Obtain at least two COD standard solutions of different concentrations, record them as standard solution S1, standard solution S2, and standard solution SN, and measure the absorbance of standard solution S1, standard solution S2, and standard solution SN, respectively.

[0051] Specifically, potassium hydrogen phthalate (KHP) is usually used to configure at least two COD standard solutions of different concentrations. The COD standard solution with a configuration concentration of C1mg / L is recorded as standard solution S1, the COD standard solution with a configuration concentration of C2mg / L is recorded as standard solution S2, and the COD standard solution concentration with a configuration concentration of CNmg / L is recorded as standard solution SN. The relationship between COD concentration and absorbance is established by detecting COD standard solutions of different concentrations. When the COD standard solution is detected through a large number of experiments, the COD concentration and absorbance are in a linear relationship. Therefore, in order to reduce the computing power requirements for the detection device, in the embodiment of the present application, the COD standard solution is used as two liquids of different concentrations, and is described based on this.

[0052] Put the standard solution S1 and the standard solution S2 as the test liquid into the detection device respectively, and obtain the absorbance of the standard solution S1 and the absorbance of the standard solution S2. According to the absorbance formula: A = -log 10 (I in / I), where A is absorbance, I in is the incident light intensity, I is the transmitted light intensity, and the absorbance of standard solution S1 and the absorbance of standard solution S2 are calculated respectively.

[0053] The detection device is used to emit detection light of at least two wavelengths to illuminate the liquid to be tested (here, the liquid to be tested is standard liquid S1 and standard liquid S2). The detection light includes ultraviolet light and visible light. The ultraviolet light and visible light can each use a wavelength within their wavelength band, or they can select wavelengths of several different bands within their wavelength band as detection light. Since the more detection lights there are, the higher the accuracy of the detection is. However, the data that the detection device needs to process also increases significantly with the increase in the number of detection lights, and the computing power requirements of the detection equipment are higher. In order to reduce the computing power requirements of the detection equipment and better ensure the detection accuracy, in the embodiment of the present application, the two wavelengths of light with a wavelength of 275nm ultraviolet light and a wavelength of 550nm visible light are used as examples for description.

[0054] The incident light intensity and transmitted light intensity of different wavelengths of detection light are measured respectively, where the incident light intensity is the illumination intensity of the detection light emitted by the detection device; the transmitted light intensity is the illumination intensity received from the other end of the test liquid (i.e., standard liquid S1 / standard liquid S2) after the detection light irradiates the test liquid. The detection device is used to alternately emit detection light of different wavelengths and collect the incident light intensity I at different wavelengths. in275 and I in550 And the transmitted light intensity I 275 and I 550, and based on the above absorbance formula, calculate the absorbance of standard solution S1 and standard solution S2 under 275nm ultraviolet light and 550nm visible light, respectively. Since COD substances do not absorb visible light, based on the above absorbance formula, it can be calculated that under 550nm visible light, the absorbance of standard solution S1 and standard solution S2 is 0; under 275nm ultraviolet light, the absorbance of standard solution S1 is A1 and the absorbance of standard solution S2 is A2, where A1 and A2 are specific values.

[0055] S200. Establishing an initial equation of COD concentration and absorbance based on COD concentration and absorbance at different COD concentrations.

[0056] Specifically, based on the characteristic that COD concentration and absorbance are linearly related, a general formula is preset to express the relationship between COD concentration and absorbance. The general formula is Y=K*X+B, where Y is the COD concentration, X is the absorbance, and K and B are constants. Based on the above description, the COD concentration C1 and absorbance A1 of the detected standard solution S1 and the COD concentration C2 and absorbance A2 of the standard solution S2 are substituted into the general formula Y=K*X+B, respectively, to obtain two sets of equations:

[0057] C1=K*A1+B;

[0058] C2=K*A2+B;

[0059] Solving the equations, we can get K = (C2-C1) / (A2-A1), B = C1-A1*K = C2-A2*K. Since A1, A2, C1 and C2 are specific values, we can solve and get K and B as specific values. The specific value of K obtained in this process is recorded as Ka, and the specific value of B is recorded as Ba. Ka and Ba are saved to obtain the initial equation of COD concentration and absorbance.

[0060] S300: Calibrate and adjust the initial equation to obtain a calibrated equation.

[0061] Specifically, it includes the following two steps:

[0062] S301. Prepare two calibration solutions with different COD concentrations, record them as calibration solution T1 and calibration solution T2, and calculate the absorbance of calibration solution T1 after deducting the effect of turbidity and the absorbance of calibration solution T2 after deducting the effect of turbidity.

[0063] Specifically, the calibration solution is a mixture of a COD standard solution and a turbidity standard solution (such as formazine turbidity standard solution), so the calibration solution contains turbidity. The COD concentration of calibration solution T1 is C3 mg / L, and the COD concentration of calibration solution T2 is C4 mg / L. When preparing the calibration solutions, to improve detection accuracy, the COD concentration of calibration solution T1 is selected to be lower or close to 0 mg / L. The COD concentration of calibration solution T2 is selected to be higher, that is, the COD concentration of calibration solution T2 is much higher than that of calibration solution T1 (C4 mg / L >> C3 mg / L).

[0064] Calibration liquid T1 and calibration liquid 2 are placed in the detection device as the test liquids, and the absorbance A3 of calibration liquid T1 after deducting the turbidity effect and the absorbance A4 of calibration liquid T2 after deducting the turbidity effect are obtained. The calculation of absorbance A3 and A4 specifically includes the following steps:

[0065] The detection device is used to alternately emit the same detection light as in step S100 to illuminate the liquid to be tested (here, the liquid to be tested is the calibration liquid T1 and the calibration liquid T2).

[0066] The incident light intensity and the transmitted light intensity of the liquid to be tested under ultraviolet light irradiation, as well as the incident light intensity and the transmitted light intensity of the liquid to be tested under visible light irradiation are respectively obtained.

[0067] Based on the above absorbance formula, the absorbance A3 of calibration solution T1 after subtracting the effect of turbidity and the absorbance A4 of calibration solution T2 after subtracting the effect of turbidity are calculated. The absorbance of the test liquid under UV light and the absorbance under visible light are calculated separately, and the absorbance of the test liquid after subtracting the effect of turbidity is obtained by subtracting the two absorbances. Since COD components only absorb UV light, and turbidity components absorb both UV and visible light, the absorbance measured by UV light is the sum of the COD and turbidity components. Therefore, the absorbance of the calibration solution after subtracting the effect of turbidity is obtained by subtracting the absorbance of the visible light from the absorbance measured by UV light.

[0068] That is, the detection device emits 275nm ultraviolet light and 550nm visible light to illuminate the calibration solution T1 and calibration solution 2 respectively, and collects the incident light intensity I at different wavelengths. in275 and I in550 And the transmitted light intensity I 275 and I 550Based on the above absorbance formula, the absorbance of calibration solution T1 and calibration solution 2 under 275nm ultraviolet light and 550nm visible light is calculated respectively. Based on the above absorbance formula, under 275nm ultraviolet light, the absorbance of calibration solution T1 is calculated to be A31, and the absorbance of calibration solution T2 is calculated to be A41; under 550nm visible light, the absorbance of calibration solution T1 is calculated to be A32, and the absorbance of calibration solution T2 is calculated to be A42. Since the COD component only absorbs ultraviolet light, and the turbidity component absorbs both ultraviolet light and visible light, the absorbance of calibration solution T1 after deducting the influence of turbidity is A3 = A31 - A32; the absorbance of calibration solution T2 after deducting the influence of turbidity is A4 = A41 - A42. Since A31, A32, A41, and A42 are specific values, A3 and A4 are also specific values.

[0069] S302 : Based on the COD concentrations of calibration solutions T1 and 2 and the absorbance after deducting the influence of turbidity, the initial equation of COD concentration and absorbance is adjusted to obtain a calibration equation of COD concentration and absorbance.

[0070] Specifically, based on the obtained initial equation of COD concentration and absorbance: Y=Ka*X+Ba (Ka and Ba are specific values), the COD concentration C3 of the calibration solution T1 and the absorbance A3 after deducting the turbidity effect are substituted into the initial equation. In order to effectively reduce the interference of turbidity on COD measurement, select calibration solution T1 with a COD concentration of 0 or close to 0, perform zero calibration on the initial equation using calibration solution T1, and substitute C3 and A3 into the initial equation, i.e. C3 = Ka*A3 + Ba. Because the COD concentration C3 of the calibration solution is approximately equal to 0, theoretically A3 is approximately equal to 0, so Ba should also be approximately equal to 0. However, in reality, the value of Ba may not be equal to 0, so Ba is corrected to Bb, Bb = C3-Ka*A3; Bb is a specific value, and Bb is used to cover and replace Ba. At this time, the equation after zero calibration is: Y = Ka*X+Bb; at the same time, the COD concentration C3 of the calibration solution T1 and the absorbance A3 after deducting the influence of turbidity are saved.

[0071] Since the COD concentration of the calibration liquid T2 is higher than that of the calibration liquid T1, and the COD concentration of the calibration liquid T2 is higher, the slope of the formula is calibrated by the calibration liquid T2, that is, the COD concentration C4 and absorbance A4 of the calibration liquid T2 and the stored data C3 and A3 are substituted into the equation Y=Ka*X+Bb after zero calibration (Ka and Bb are specific values), and two sets of equations can be obtained:

[0072] C3=Ka*A3+Bb;

[0073] C4=Ka*A4+Bb;

[0074] From this, we can calculate Kc = (C4-C3) / (A4-A3); Bc = C3-A3*Kc, where Kc and Bc are specific values. Kc replaces Ka and Bc replaces Bb for overwriting and storage. After zero calibration and slope calibration, the calibration equation for COD concentration and absorbance is obtained: Y = Kc*X+Bc (Kc and Bc are specific values).

[0075] S400: Substitute the calibration equation as the initial equation, re-obtain the COD standard solution, and repeat step S300.

[0076] Specifically, the calibration equation is a non-fixed equation, i.e., the Kc and Bc calculated in step S302 are not fixed. The calibration equation is repeated along with the calibration adjustment operation. In continuous calibration calculation, the error of the instrument (i.e., detection device) is corrected, the influence of time and environment is offset. After the instrument has been operated for a long time, factors such as electronic component aging and temperature fluctuations may affect the detection accuracy of the instrument. After a calibration adjustment is completed, the calibration equation obtained by calculating is used as the initial equation to replace the original initial equation. When the COD standard solution is subsequently obtained, the calibration adjustment operation of step S300 is repeated to calculate new Kd and Bd to replace the original Kc and Bc, thereby obtaining a new calibration equation.

[0077] During the actual calibration operation, the user pours the test liquid with unknown COD concentration into the detection device. By alternately turning on and off two different wavelengths of detection light, each acquisition receiver receives the corresponding light intensity signal, and uses the difference between the on and off values ​​as the representative value of the light intensity of the test liquid at the corresponding wavelength. The absorbance at the two wavelengths is calculated, and then the absorbance of the COD component at the ultraviolet wavelength is calculated. By substituting the absorbance of the COD component of the test liquid at the ultraviolet wavelength into the calibration equation, the COD concentration of the test liquid can be calculated.

[0078] At the same time, in order to ensure that the detection device can be directly tested and used by the actual user after the equipment is delivered, the detection device can obtain a calibration equation that can be directly applied through multiple repeated calibration operations when leaving the factory. Similarly, the user can calculate the calibration equation by himself, and in the later use process, the user can also repeat the calibration adjustment operation to calibrate and adjust the calibration equation of the detection device.

[0079] S410: Accumulate the number of calibration adjustments and determine whether the number of calibration adjustments reaches a preset value.

[0080] Specifically, to improve the detection accuracy of the detection device, before the detection device is actually used, the calibration equation is calibrated and adjusted multiple times so that the final calibration equation of the detection device can achieve higher detection accuracy during detection and reduce the impact of turbidity on the detection accuracy.

[0081] Since the values of K and B are affected by the conditions of the instrument and equipment itself (such as aging degree, differences in factory performance, assembly tolerances, etc.) and the influence of the environment on the light transmission degree of the light-transmitting lens, the process of obtaining the calibration equation by calibrating and adjusting the initial equation is recorded as one calibration adjustment. Through multiple calibration adjustments, the expression of the calibration equation for the relationship between COD concentration and absorbance can be effectively improved.

[0082] The number of calibration adjustments is recorded as N, and the initial value of N is 0. When the detection device completes one calibration adjustment of the initial equation to obtain the calibration equation, the number of calibration adjustments is accumulated, resulting in N = N + 1. The number of calibration adjustments can be manually selected whether to reset the data, that is, to clear all previous records of the number of calibration adjustments.

[0083] The preset value is set as M, and M is a specific value, which can be 3, 5, 10, 50, 100, etc., and there is no limit to this. The selection of the preset value M is based on the tests of multiple detection devices. Generally, when choosing the number of calibration adjustments, the number of times when the calibration equation reaches a stable state is used as M, or several times are added based on the number of times when the calibration equation reaches a stable state as M. The calibration equation reaches a stable state when: the new calibration equation is the same as the initial equation before its calibration adjustment, that is, it can be considered that the calibration equation reaches a stable state.

[0084] S420. If the number of calibration adjustments is less than the preset value, the calibration equation of the COD concentration and absorbance is used as the new initial equation, and step S300 is returned.

[0085] Specifically, when N < M, it means that the detection device believes that the calibration equation has not reached a stable state. At this time, the calibration equation obtained in step S300 is used as the initial equation, that is, this initial equation is substituted into the initial equation required for calculation in step S300, and the process described in step S300 is looped. According to the description in step S300, two calibration solutions with different COD concentrations need to be configured for this process. To enable the calibration equation to better deduct the influence of turbidity, the concentrations of these two calibration solutions are preferably in a ratio inconsistent with the turbidity concentration of the previous calibration solution. In order to reduce the complexity of the experiment, it is preferably that in adjacent two calibration adjustment steps, the turbidity concentration ratios of the calibration solutions are inconsistent.

[0086] S430: If the calibration adjustment times are greater than or equal to the preset value, the calibration equation of COD concentration and absorbance is saved as the final relationship equation of COD concentration and absorbance.

[0087] Specifically, when N=M, it is determined that the number of calibration adjustments has reached a preset value. At this time, the detection device believes that the calibration equation has reached a stable state and uses the calibration equation as the final relationship between COD concentration and absorbance. This allows the detection device to detect the absorbance of the liquid to be tested and substitute the absorbance into this relationship during actual use to calculate the COD concentration of the liquid to be tested.

[0088] Furthermore, in actual use, by placing the liquid to be tested in the detection environment of the detection device, the detection device is used to emit 275nm ultraviolet light and 550nm visible light to illuminate the liquid to be tested, and the incident light intensity I at different wavelengths is collected respectively. in275 and I in550 And the transmitted light intensity I 275 and I 550 , and based on the above absorbance formula, the absorbance of the liquid to be tested under 275nm ultraviolet light and 550nm visible light. Based on the above absorbance formula, the absorbance of the liquid to be tested under 275nm ultraviolet light is calculated to be An1; the absorbance of the liquid to be tested under 550nm visible light is calculated to be An2. Therefore, it can be known that the absorbance of the liquid to be tested after deducting the influence of turbidity is An=An1-An2; An1, An2 and An are specific values. Substitute An into the calibration equation Y=Kc*X+Bc. Since Kc and Bc are specific values, after An replaces X, the value of Y can be calculated. That is, by obtaining the absorbance of the liquid to be tested after deducting the influence of turbidity, the COD concentration of the liquid to be tested can be quickly obtained using the calibration equation.

[0089] The present application also discloses a UV COD detection system with turbidity compensation. Figure 3 The UV COD detection system includes a detection device 1 and a display device 2; the detection device 1 is used to measure the COD concentration of the liquid and output the detection result; the display device 2 is used to receive and display the detection result output by the detection device 1. The display device 2 can be a display screen, a mobile phone or other display, so that the user can obtain the detection result of the corresponding liquid to be tested.

[0090] The detection device 1 comprises:

[0091] Optical path module 11: equipped with an emitting light source 111 with at least two wavelengths and a light intensity receiving group 112 arranged in a one-to-one correspondence with the emitting light source 111; the emitting light source 111 is used to emit detection light of the required wavelength to illuminate the liquid to be tested; the light intensity receiving group 112 is used to obtain the light intensity information of the detection light, which includes two receivers, one of which is used to measure the incident light intensity and the other is used to measure the transmitted light intensity.

[0092] The main control module 12 is used to output a digital control signal to control the light source 111 to emit detection light intensity, receive light intensity information measured by the light intensity receiving group 112, and calculate the COD concentration based on the light intensity information.

[0093] The signal processing module 13 is used to receive the digital control signal output by the main control module 12 and convert the digital control signal into an analog control signal and output it to the optical path module 11 . At the same time, the light intensity information collected by the light intensity receiving group 112 is converted into a voltage signal and transmitted to the main control module 12 .

[0094] The data transmission module 14 is used to transmit the detection results calculated by the main control module 12 , for example, output the detection results to the display device 2 .

[0095] Specifically, the optical path module 11 is installed on a liquid container. The liquid container is a container for holding the liquid to be tested. It has good light transmittance and chemical inertness, and is not easy for the liquid to be tested to undergo chemical reactions. The liquid container can be fixed as a part of the detection device 1, or it can be configured separately. No specific limitation is made in this application. The emitting light source 111 is used to emit detection light, which includes an ultraviolet light source and a visible light source. As described above, in the embodiment of this application, the emitting light source 111 is described as an example of two wavelength light sources. One emitting light source 111 is an ultraviolet light source with a wavelength of 275nm, and the other emitting light source 111 is a visible light source with a wavelength of 550nm.

[0096] Furthermore, in some embodiments, in order to prevent light of other wavelengths from entering and causing interference and resulting in measurement errors, the optical path module 11 also includes a filter. The filter is arranged at the output end of the emitting light source 111 to filter the light output by the emitting light source 111. The filter can be a narrow-band filter, such as a narrow-band filter, which can effectively filter out all light other than a specific wavelength, thereby ensuring that the light irradiating the liquid is light of a specific wavelength, thereby making the measurement more accurate and the error smaller.

[0097] When the liquid to be tested needs to be inspected, a digital control signal is sent through the main control module 12. The signal processing module 13 converts the digital control signal into an analog control signal and sends it to the optical path module 11, so that the emitting light source 111 outputs a corresponding intensity of detection light to illuminate the liquid to be tested. The light intensity receiving group 112 obtains light intensity information. Specifically, the two receivers respectively obtain the incident light intensity and the transmitted light intensity based on their positional relationship with the light source. The incident light intensity and the transmitted light intensity are converted into current signals and output to the signal processing module 13. The signal processing module 13 processes the corresponding current signals into voltage signals that can be collected and processed by the main control module 12.

[0098] In the embodiment of the present application, the amount of calculation during COD concentration detection can be greatly reduced by the above-mentioned COD concentration detection method, so the main control module 12 adopts a single-chip microcomputer to meet the calculation requirements, and the main control module 12 can adopt common single-chip microcomputer models such as ADUCM361. In actual use, the main control module 12 is responsible for receiving and processing the light intensity information output by the optical path module 11. By executing a pre-stored algorithm program, the COD concentration of the liquid to be tested is calculated according to the received light intensity information. This can effectively avoid using high-calculation methods such as AI, concentration learning, and linear fitting, reduce the complexity of the algorithm, and be conducive to implementation in a single-chip microcomputer. At the same time, due to the low amount of calculation, this solution can enable the detection of COD concentration to achieve on-site rapid detection and online detection. In this solution, by adopting light sources with two wavelengths of visible light and ultraviolet light to irradiate the liquid to be tested, the visible light signal is used to compensate for turbidity to improve the accuracy of detection. The pre-stored algorithm program is the calibration equation obtained in the above-mentioned COD concentration detection method. At the same time, the main control module 12 is also used to execute steps S100-S600 in the above-mentioned COD concentration detection method to obtain a calibration equation.

[0099] The data transmission module 14 includes a communication device. When the main control module 12 calculates the COD concentration of the liquid to be tested based on the calibration equation and the absorbance of the liquid to be tested, the data transmission module 14 outputs the test result to the display device 2 in a signal transmission mode, and the user can observe the test result of the liquid to be tested on the display device 2 in real time.

[0100] Of course, the UV COD detection system is also equipped with a power supply to provide the required electrical energy for the operation of the entire system. The power supply can be a storage battery or directly connected to the mains.

[0101] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A UV COD detection method with turbidity compensation, characterized in that: The following steps are involved: S100, obtaining at least two COD standard solutions of different concentrations, denoted as standard solution S1, standard solution S2, and standard solution SN, and measuring the absorbance of the standard solution S1, the standard solution S2, and the standard solution SN, respectively; S200, establishing an initial equation of COD concentration and absorbance based on the COD concentration and absorbance of the COD standard solutions of different concentrations; S300, calibrating and adjusting the initial equation to obtain a calibration equation, wherein the calibration equation is a relationship equation between COD concentration and absorbance; S400: Substitute the calibration equation as the initial equation, re-obtain the COD standard solution, and repeat step S300.

2. the UV method COD detection method with turbidity compensation according to claim 1, is characterized in that: Based on the COD concentration and absorbance of the COD standard solutions of different concentrations, an initial equation of COD concentration and absorbance is established, comprising the following steps: Substituting the obtained COD concentration and absorbance of the standard solution into the general formula Y=K*X+B respectively to obtain at least two sets of equations, wherein Y is the COD concentration, X is the absorbance, and K and B are both constants; The specific values ​​of K and B were solved through the equation system and substituted into the general formula to obtain the initial equation of COD concentration and absorbance.

3. the UV method COD detection method with turbidity compensation according to claim 1, is characterized in that: The calibration adjustment of the initial equation to obtain the calibration equation includes the following steps: Prepare two calibration solutions with different COD concentrations, record them as calibration solution T1 and calibration solution T2, and calculate the absorbance of the calibration solution T1 after deducting the effect of turbidity and the absorbance of the calibration solution T2 after deducting the effect of turbidity respectively; Based on the COD concentrations of the calibration solutions T1 and T2 and the absorbance after deducting the influence of turbidity, the initial equation of COD concentration and absorbance is adjusted to obtain a calibration equation of COD concentration and absorbance by calculation.

4. the UV method COD detection method with turbidity compensation according to claim 3 is characterized in that: Calculating the absorbance of the calibration solution T1 after deducting the effect of turbidity and the absorbance of the calibration solution S2 after deducting the effect of turbidity; comprising: Obtaining the incident light intensity and the transmitted light intensity of the calibration solution under ultraviolet light irradiation, and the incident light intensity and the transmitted light intensity of the calibration solution under visible light irradiation; Based on the incident light intensity and transmitted light intensity obtained, the absorbance of the calibration solution under ultraviolet light and the absorbance under visible light are calculated respectively, and the absorbance of the calibration solution after deducting the influence of turbidity can be obtained by subtracting the two.

5. the UV method COD detection method with turbidity compensation according to claim 3 is characterized in that: Based on the COD concentrations of the calibration solution T1 and the calibration solution 2 and the absorbance after deducting the influence of turbidity, adjusting the initial equation of the COD concentration and absorbance, and calculating the calibration equation of the COD concentration and absorbance, comprising the following steps: Zero calibration: Substitute the COD concentration C3 of the calibration solution T1 and the absorbance A3 after deducting the influence of turbidity into the initial equation and correct the constant B by calculation; Slope calibration: Substitute the COD concentration C4 and absorbance A4 of the calibration solution T2, as well as the COD concentration C3 and absorbance A3 after deducting the influence of turbidity of the calibration solution T1 into the equation after zero calibration, and correct the constant K by calculation.

6. The UV COD detection method with turbidity compensation according to claim 5, wherein: The COD concentration C3 of the calibration solution T1 is close to 0 mg / L; the COD concentration C4 of the calibration solution T2 is much greater than C3.

7. The UV COD detection method with turbidity compensation according to claim 1, wherein: During two adjacent calibration adjustments, the turbidity concentration ratio of the calibration solution is inconsistent.

8. A UV COD detection system with turbidity compensation according to any one of claims 1 to 7, characterized in that: The UV COD detection system includes a detection device and a display device; The detection device is used to measure the COD concentration of the liquid and output the detection result; The display device is used to receive and display the detection result of the detection device.

9. The UV COD detection system with turbidity compensation according to claim 8, characterized in that: The detection device comprises: An optical path module (11) is configured with an emitting light source (111) of at least two wavelengths and a light intensity receiving group (112) arranged in a one-to-one correspondence with the emitting light source (111); the emitting light source (111) is used to emit detection light of a required wavelength; the light intensity receiving group (112) is used to obtain light intensity information of the detection light; A main control module (12) is used to output a digital control signal for controlling the emission light source (111) to emit a detection light intensity, and to receive light intensity information measured by the light intensity receiving group (112), and to calculate the COD concentration based on the light intensity information; A signal processing module (13) is configured to receive a digital control signal output by the main control module (12) and convert the digital control signal into an analog control signal and output it to the optical path module (11); and simultaneously convert the light intensity information collected by the light intensity receiving group (112) into a voltage signal and output it to the main control module (12); Data transmission module (14): used for transmitting the detection result calculated by the main control module (12).

10. The UV COD detection system with turbidity compensation according to claim 9, characterized in that: The optical path module (11) further comprises a filter, which is arranged at the output end of the emitting light source (111) and is used to filter light; The light intensity receiving group (112) includes two receivers, one of which is used to measure the incident light intensity of the detection light, and the other is used to measure the transmitted light intensity.

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