A total phosphorus online monitoring compensation method applicable to turbidity samples

Abstract

The patent of the present invention relates to an online monitoring compensation method, and more particularly to an online monitoring compensation method for total phosphorus that can be applied to turbidity samples. Proceed in the following steps: prepare an interference model that effectively simulates an actual turbidity water sample → prepare a mixed standard of total phosphorus and turbidity. The turbidity compensation method provided by the present invention can effectively detect the total phosphorus concentration within 500NTU turbidity at different particle sizes, and the error is less than ±10%, and the turbidity spike recovery is between 90%-110%, which improves the adaptability of total phosphorus monitoring under different complex water qualities.

Description

Technical Field

[0001] The invention relates to an online monitoring compensation method, and more particularly to an online monitoring compensation method for total phosphorus that can be applied to turbidity samples. Background Art

[0002] With the development of various aspects, the pollution to the environment is becoming more and more serious. The pollution of water resources will directly affect the living environment and health of human beings. The protection of the environment has been paid more and more attention by the country. The protection of the environment should start from prevention and governance, among which water resources are an important aspect. In order to understand the water quality of the water body, it is necessary to sample and analyze the water body. The online water quality monitor is an instrument that can realize automatic sampling and analysis of water bodies. It can be installed near the water body and transmit the collected data to environmental monitoring stations and other departments for monitoring.

[0003] Total phosphorus is the total content of phosphorus in water. Excessive phosphorus content will cause excessive growth of algae, eutrophication of water bodies, algal blooms or red tides, and disrupt the balance of water bodies. In recent years, as the country has strengthened its environmental protection efforts, total phosphorus has also been listed as a major pollutant. Various environmental monitoring water stations have been gradually installed in important rivers and lakes. However, online water quality monitoring faces many technical difficulties, among which turbidity interference is the most difficult point in online monitoring of total phosphorus, especially in dealing with complex working conditions such as the Yellow River water quality and river water after heavy rain.

[0004] Existing technical solutions:

[0005] There are mainly the following technical solutions for total phosphorus water with different turbidity:

[0006] 1) Treat water samples by natural sedimentation, large mesh sieve filtration, etc., and take the supernatant to analyze the total phosphorus in water quality;

[0007] 2) Use parallel samples for absorbance subtraction: that is, test two groups of water samples, one group adds an equal amount of reagent that does not react with it, and the other group adds a complete reaction reagent. The absorbance of the latter at 700nm minus the absorbance of the former at 700nm is taken as the final absorbance of the sample, and then the absorbance is used to enter the standard curve to calculate the concentration;

[0008] Disadvantages of existing technology:

[0009] 1) The traditional 700nm is used as the characteristic wavelength for total phosphorus determination, which has relatively low sensitivity;

[0010] 2) The experimental interference model setting for the turbidity solution does not conform to the actual turbidity form of the water body; (generally, the standard turbidity solution (hexamethylenetetramine + hydrazine sulfate) is used. The online monitoring of total phosphorus contains oxidants. The standard turbidity solution is easily oxidized by the oxidants and loses the significance of experimental interference)

[0011] 3) For high turbidity water samples, natural sedimentation, filtration and other means are usually used to remove turbidity before monitoring total phosphorus. However, most of the phosphorus in natural water bodies is attached to water particles (turbidity), which in turn affects the accuracy of total phosphorus data.

[0012] 4) The traditional method uses parallel samples to compensate for the total phosphorus concentration containing turbidity, which is not suitable for online monitoring of total phosphorus water quality. Summary of the invention

[0013] The present invention mainly solves the deficiencies in the prior art and provides a method for effectively detecting the total phosphorus concentration within 500 NTU turbidity at different particle sizes, with an error of less than ±10%, and a turbidity spike recovery of between 90% and 110%. The method improves the adaptability of total phosphorus monitoring under different complex water qualities and is a total phosphorus online monitoring compensation method applicable to turbidity samples.

[0014] The above technical problems of the present invention are mainly solved by the following technical solutions:

[0015] A total phosphorus online monitoring compensation method applicable to turbidity samples is carried out in the following steps:

[0016] (1) Prepare an interference model that effectively simulates actual turbidity water samples;

[0017] ① White clay is used to simulate the turbidity components of actual water samples. First, white clay has adsorption properties, and the total phosphorus in the water body is easily adsorbed on the particulate matter. Second, white clay is insoluble in water, acid and alkali, so it is not easy to be reacted in the subsequent total phosphorus and turbidity liquid mixed standard test process and loses its interference significance;

[0018] ② Preparation of total phosphorus turbidity interference components: weigh 10g of white clay with three mesh sizes of 200 mesh, 600 mesh and 1250 mesh as turbidity mother solution;

[0019] 200 mesh, 600 mesh and 1250 mesh represent different particle sizes of particles. The larger the mesh number, the smaller the particle size.

[0020] ③ Take 50 mL of total phosphorus oxidant respectively and heat and oxidize the three kinds of white clay with different particle sizes until the oxidant is completely volatilized and the white clay becomes sticky. After cooling, add 800 mL of phosphorus-free distilled water;

[0021] ④ Seal the above three suspensions and let them stand for 3 to 7 days, observe the changes in the supernatant, and after the supernatant is completely clear, take a small amount of the supernatant to test its total phosphorus concentration;

[0022] ⑤ If the total phosphorus concentration of the supernatant is ≤0.1mg / L, pour out the supernatant, add distilled water to the white clay and a small amount of suspension at the bottom to make up to 1000mL, transfer to a wide-mouth bottle for storage, and record it as the turbidity mother solution;

[0023] ⑥If the total phosphorus concentration of the supernatant is > 0.1 mg / L, repeat steps ②→③→④;

[0024] ⑦The above preparation process can effectively remove the total phosphorus substances in the white clay;

[0025] (2) Preparation of total phosphorus and turbidity mixed standard:

[0026] 890nm was selected as the characteristic wavelength for total phosphorus monitoring, and 1050nm, which is also in the infrared band, was used as the turbidity compensation wavelength;

[0027] ①Prepare total phosphorus standard solutions of known concentrations: 0.2 mg / L and 1.6 mg / L;

[0028] ② Dilute the different mesh turbidity mother solutions prepared in step (1) respectively to form:

[0029] 200 mesh (100NUT / 200NTU / 300NTU / 400NTU / 500NTU),

[0030] 600 mesh (100NUT / 200NTU / 300NTU / 400NTU / 500NTU) and

[0031] 1250 mesh (100NUT / 200NTU / 300NTU / 400NTU / 500NTU);

[0032] ③ Use the turbidity solution diluted in step (2) to prepare phosphorus-containing solutions: 0.2 mg / L and 1.6 mg / L, thus obtaining a total phosphorus and turbidity mixed standard;

[0033] ④ Determine the solutions prepared in steps ①, ②, and ③, and detect their absorbance at 890 nm and 1050 nm before and after color development, respectively, and record them as I890 before color development, I1050 before color development, I890 after color development, and I1050 after color development;

[0034] The absorbance algorithm is: A = log (I890 before color development / I890 after color development) - log (I1050 before color development / I1050 after color development);

[0035] ⑤ Using the standard solution as a reference, calculate the relative error between total phosphorus and gradient turbidity mixed standard, that is, the accuracy of total phosphorus + gradient turbidity mixed standard; spike recovery rate, that is, the recovery rate of the gradient turbidity solution when phosphorus standard solution is added.

[0036] Because total phosphorus detection has absorption in the 200-1100nm wavelength range, but less absorption in the infrared wavelength range (860nm-1100nm), Figure 1 It can be seen that the absorption peak of the total phosphorus coloring substance at 890nm is 20% higher than the absorption peak at 700nm, and tends to be stable after 1050nm. Therefore, 890nm is selected as the characteristic wavelength for total phosphorus determination, and 1050nm is selected as the turbidity compensation wavelength.

[0037] Purpose of the present invention:

[0038] 1) Provide an interference model that effectively simulates turbidity water samples on site to verify the reliability of the total phosphorus online monitoring compensation method;

[0039] 2) 890nm is used as the characteristic absorption wavelength of total phosphorus, which improves the sensitivity of total phosphorus determination and reduces the interference caused by turbidity;

[0040] 3) Using 1050nm, which is also in the infrared band, as the turbidity compensation wavelength;

[0041] 4) Taking the above interference model as the experimental object, the accuracy and turbidity spike recovery rate were determined using a total phosphorus online monitor, which could meet the technical requirements of the enterprise standard indication error of ±10% and spike recovery rate of 90%-110%;

[0042] 5) It can support the determination of total phosphorus in water samples with a maximum turbidity of 500 NTU. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is the absorption spectrum of the total phosphorus color-developing substance of the present invention at 200-1100nm;

[0044] Figure 2 It is a schematic diagram of the total phosphorus + turbidity gradient mixed standard concentration value, indication error and spike recovery at 200 mesh in the present invention;

[0045] Figure 3 It is a schematic diagram of the total phosphorus + turbidity gradient mixed standard concentration value, indication error and spike recovery at 600 mesh in the present invention;

[0046] Figure 4 It is a schematic diagram of the total phosphorus + turbidity gradient mixed standard concentration value, indication error and spike recovery at 1250 mesh in the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0048] Example 1: 200 mesh: total phosphorus and gradient turbidity mixed standard, relative error and spike recovery;

[0049] According to the absorbance algorithm described in ④ in the above step (2), 0.2 mg / L (No. 1), 1.6 mg / L (No. 2), 100 NTU (200 mesh) turbidity solution (No. 3), 0.2 mg / L + 100 NTU (200 mesh) total phosphorus + turbidity mixed standard (No. 4), 1.6 mg / L + 100 NTU (200 mesh) total phosphorus + turbidity mixed standard (No. 5), 200 NTU (200 mesh) turbidity solution (No. 6), 0.2 mg / L + 200 NTU (200 mesh) total phosphorus + turbidity mixed standard (No. 7), 1.6 mg / L / 200 NTU (200 mesh) total phosphorus + turbidity mixed standard (No. 8), 300 NTU (200 mesh) turbidity solution (No. 9), 0. .2mg / L+300NTU(200 mesh) total phosphorus + turbidity mixed standard (No. 10), 1.6mg / L+300NTU(200 mesh) total phosphorus + turbidity mixed standard (No. 11), 400NTU(200 mesh) turbidity solution (No. 12), 0.2mg / L+400NTU(200 mesh) total phosphorus + turbidity mixed standard (No. 13), 1.6mg / L+400NTU(200 mesh) total phosphorus + turbidity mixed standard (No. 14), 500NTU(200 mesh) turbidity solution (No. 15), 0.2mg / L+500NTU(200 mesh) total phosphorus + turbidity mixed standard (No. 16), 1.6mg / L+500NTU(200 mesh) total phosphorus + turbidity mixed standard (No. 17);

[0050] Calculate the corresponding concentration value based on the absorbance and standard curve, and then make relative error with the concentration value of 0.2mg / L (No. 1) and 1.6mg / L (No. 2) standard solution; make spike recovery rate with the concentration value of turbidity solution, see Figure 2 ;

[0051] Example 2: 600 mesh: total phosphorus and gradient turbidity mixed standard, relative error and spike recovery;

[0052] According to the absorbance algorithm described in step (2) ④, 0.2 mg / L (No. 1), 1.6 mg / L (No. 2), 100 NTU (600 mesh) turbidity solution (No. 18), 0.2 mg / L + 100 NTU (600 mesh) total phosphorus + turbidity mixed standard (No. 19), 1.6 mg / L + 100 NTU (600 mesh) total phosphorus + turbidity mixed standard (No. 20), 200 NTU (600 mesh) turbidity solution (No. 21), 0.2 mg / L + 200 NTU (600 mesh) total phosphorus + turbidity mixed standard (No. 22), 1.6 mg / L / 200 NTU (600 mesh) total phosphorus + turbidity mixed standard (No. 23), 300 NTU (600 mesh) turbidity solution (No. 24) were measured respectively. No.), 0.2mg / L+300NTU(600 mesh) total phosphorus + turbidity mixed standard (No. 25), 1.6mg / L+300NTU(600 mesh) total phosphorus + turbidity mixed standard (No. 26), 400NTU(600 mesh) turbidity solution (No. 27), 0.2mg / L+400NTU(600 mesh) total phosphorus + turbidity mixed standard (No. 28), 1.6mg / L+400NTU(600 mesh) total phosphorus + turbidity mixed standard (No. 29), 500NTU(600 mesh) turbidity solution (No. 30), 0.2mg / L+500NTU(600 mesh) total phosphorus + turbidity mixed standard (No. 31), 1.6mg / L+500NTU(600 mesh) total phosphorus + turbidity mixed standard (No. 32);

[0053] Calculate the corresponding concentration value based on the absorbance and standard curve, and then make relative error with the concentration value of 0.2mg / L (No. 1) and 1.6mg / L (No. 2) standard solution; make spike recovery rate with the concentration value of turbidity solution, see Figure 3 ;

[0054] Example 3: 1250 mesh: Gradient turbidity mixed standard of total phosphorus, relative error and spike recovery;

[0055] According to the absorbance algorithm described in ④ in the above step (2), 0.2 mg / L (No. 1), 1.6 mg / L (No. 2), 100 NTU (1250 mesh) turbidity solution (No. 33), 0.2 mg / L + 100 NTU (1250 mesh) total phosphorus + turbidity mixed standard (No. 34), 1.6 mg / L + 100 NTU (1250 mesh) total phosphorus + turbidity mixed standard (No. 35), 200 NTU (1250 mesh) turbidity solution (No. 36), 0.2 mg / L + 200 NTU (1250 mesh) total phosphorus + turbidity mixed standard (No. 37), 1.6 mg / L / 200 NTU (1250 mesh) total phosphorus + turbidity mixed standard (No. 38), 300 NTU (1250 mesh) turbidity solution (No. 39) were respectively determined. )、0.2mg / L+300NTU(1250mesh) total phosphorus + turbidity mixed standard (No. 40)、1.6mg / L+300NTU(1250mesh) total phosphorus + turbidity mixed standard (No. 41)、400NTU(1250mesh) turbidity liquid (No. 42)、0.2mg / L+400NTU(1250mesh) total phosphorus + turbidity mixed standard (No. 43)、1.6mg / L+400NTU(1250mesh) total phosphorus + turbidity mixed standard (No. 44)、500NTU(1250mesh) turbidity liquid (No. 45)、0.2mg / L+500NTU(1250mesh) total phosphorus + turbidity mixed standard (No. 46)、1.6mg / L+500NTU(1250mesh) total phosphorus + turbidity mixed standard (No. 47);

[0056] Calculate the corresponding concentration value based on the absorbance and standard curve, and then make relative error with the concentration value of 0.2mg / L (No. 1) and 1.6mg / L (No. 2) standard solution; make spike recovery rate with the concentration value of turbidity solution, see Figure 4 ;

[0057] The turbidity compensation method provided by the present invention can effectively detect the total phosphorus concentration within 500NTU turbidity at different particle sizes, and the error is less than ±10%, and the turbidity spike recovery is between 90% and 110%, which improves the adaptability of total phosphorus monitoring under different complex water qualities.

Claims

1. A total phosphorus online monitoring compensation method applicable to turbidity samples, characterized in that Follow these steps: (1) Prepare an interference model that effectively simulates actual turbidity water samples; ① White clay is used to simulate the turbidity components of actual water samples. First, white clay has adsorption properties, and the total phosphorus in the water body is easily adsorbed on particulate matter. Second, white clay is insoluble in water, acid and alkali, so it is not easy to be reacted in the subsequent total phosphorus and turbidity liquid mixed standard test process and loses its interference significance; ② Preparation of total phosphorus turbidity interference components: weigh 10g of white clay with three mesh sizes of 200 mesh, 600 mesh and 1250 mesh as turbidity mother solution; 200 mesh, 600 mesh and 1250 mesh represent different particle sizes of particles. The larger the mesh number, the smaller the particle size. ③ Take 50 mL of total phosphorus oxidant respectively and heat and oxidize the three kinds of white clay with different particle sizes until the oxidant is completely volatilized and the white clay is in a sticky state. After cooling, add 800 mL of phosphorus-free distilled water to obtain a suspension; ④ Seal the above three suspensions and let them stand for 3 to 7 days, observe the changes in the supernatant, and after the supernatant is completely clear, take a small amount of the supernatant to test its total phosphorus concentration; ⑤ If the total phosphorus concentration of the supernatant is ≤0.1mg / L, pour out the supernatant, add distilled water to the white clay and a small amount of suspension at the bottom to make up to 1000mL, transfer to a wide-mouth bottle for storage, and record it as the turbidity mother solution; ⑥If the total phosphorus concentration of the supernatant is > 0.1 mg / L, repeat steps ②→③→④; ⑦The above preparation process can effectively remove the total phosphorus substances in the white clay; (2) Preparation of total phosphorus and turbidity mixed standard: 890nm was selected as the characteristic wavelength for total phosphorus monitoring, and 1050nm, which is also in the infrared band, was used as the turbidity compensation wavelength; a. Prepare total phosphorus standard solutions of known concentrations: 0.2 mg / L and 1.6 mg / L; b. Dilute the different mesh turbidity mother solutions prepared in step (1) to form: 200 mesh, turbidity is 100NTU, 200NTU, 300NTU, 400NTU and 500NTU; 600 mesh, turbidity of 100NTU, 200NTU, 300NTU, 400NTU and 500NTU; and, 1250 mesh, turbidity is 100NTU, 200NTU, 300NTU, 400NTU and 500NTU; c. Prepare phosphorus-containing solutions using the turbidity solution diluted in step (2) b: 0.2 mg / L and 1.6 mg / L, to obtain a total phosphorus and turbidity mixed standard; d. Determine the solution prepared in steps a, b, and c, and detect the absorbance at 890 nm and 1050 nm before and after color development, respectively, recorded as I890 before color development, I1050 before color development, I890 after color development, and I1050 after color development; The absorbance algorithm is: A=log (I890 before color development / I890 after color development)-log (I1050 before color development / I1050 after color development); e. Using the standard solution as a reference, calculate the relative error between total phosphorus and gradient turbidity mixed standard, that is, the accuracy of total phosphorus + gradient turbidity mixed standard; spike recovery rate, that is, the recovery rate of the gradient turbidity solution when phosphorus standard solution is added.

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