Method for determining generation potential of nitrogenous disinfection by-product in amino acid chlorination process

Abstract

The invention discloses a method for determining the generation potential of nitrogenous disinfection by-products in an amino acid chlorination process, and belongs to the field of water body detection. The determination method comprises the following steps: S1, taking amino acid as a nitrogen source to form a sample solution, and adjusting the pH value of the sample solution; s2, chloride is added, and the chlorine adding amount and the culture time are determined; s3, determining the concentration of nitrogen-containing disinfection byproducts in the sample solution, wherein the nitrogen-containing disinfection byproducts comprise halogenated acetonitrile, halogenated nitromethane and halogenated acetamide; s4, measuring the concentration of the nitrogen-containing disinfection by-product / the concentration of the amino acid, wherein the obtained result is the generation potential of the corresponding nitrogen-containing disinfection by-product; by determining the chlorine dosage calculation formula of the chlorination reaction in the determination mode of the generation potential of the nitrogen-containing disinfection by-products, the generation potential of various nitrogen-containing disinfection by-products in the free amino acid chlorination process can be accurately evaluated, and the repeatability and reliability of the determination result are convenient for data comparison and verification among different laboratories.

Description

Technical Field

[0001] The present invention belongs to the field of water body detection, and particularly relates to a method for determining the formation potential of nitrogen-containing disinfection by-products during the chlorination of amino acids. Background Art

[0002] With the increasing attention of society to the safety of drinking water, the research on water disinfection by-products (DBPs) has made rapid progress. So far, more than 700 kinds of disinfection by-products have been identified. Among them, trihalomethanes (THMs) and haloacetic acids (HAAs) are the main categories of organic disinfection by-products in drinking water and are considered to have cytotoxicity, genotoxicity and carcinogenicity. However, current research has found that the harm caused by some new disinfection by-products to the human body may be much greater than that of trihalomethanes (THMs) and haloacetic acids (HAAs). Nitrogen-containing disinfection by-products (N-DBPs) in drinking water, including haloacetonitriles (HANs), halonitromethanes (HNMs) and haloacetamides (HAMs), etc., may have higher cytotoxicity and genotoxicity and are the key driving factors for cytotoxicity in drinking water.

[0003] Nitrogen source is a prerequisite for the formation of N-DBPs, and various free amino acids are considered to be the key precursors for the formation of various N-DBPs. In source water, free amino acids are usually 1 / 10 of the size of bound amino acids, with an average concentration of about 406 nmol / L (about 52 μg / L). Although the concentration of free amino acids in source water is lower than that of bound amino acids, studies have shown that the molar yield of free amino acids forming N-DBPs is higher. Therefore, it is urgent to develop effective methods to control the formation of N-DBPs during the chlorination of free amino acids.

[0004] The control of the formation of N-DBPs during the chlorination of free amino acids can be divided into three approaches: (1) Source control: Control the content of free amino acids or DBP precursors in the water source before disinfection to avoid the generation of N-DBPs from the source; (2) Process control: Adjust the water disinfection process to reduce the formation amount of N-DBPs; (3) End control: Directly remove the N-DBPs that have been formed after disinfection. In source control, it is difficult for conventional processes to effectively remove free amino acids in the water source, and the removal rate is only 40%. In process control, due to the complex and diverse formation mechanisms of N-DBPs, it is difficult for water plants to find a suitable disinfection process to comprehensively control the formation of N-DBPs. In end control, once N-DBPs are formed, they are difficult to remove, and since the precursors of N-DBPs still exist, even if the water plant has removed the N-DBPs in the water after disinfection, it is very likely that N-DBPs will be formed again under certain subsequent suitable conditions. Therefore, removing the precursors of N-DBPs in the water to the greatest extent possible is the relatively most effective method, and the formation potential (FP) of N-DBPs is usually used to characterize the content level of such precursors.

[0005] At present, the determination methods of the formation potential (FP) of N-DBPs are continuously optimized, such as optimizing the chlorine dosage, disinfection time, and combined factors of pH-temperature, etc., to improve the accuracy of FP testing. However, the research on the optimal FP testing models for various N-DBPs during the chlorination of free amino acids is still in the development stage. Future research needs to further explore the influence of different factors on FP and develop more accurate and efficient FP testing models to better evaluate and control the formation of N-DBPs during the chlorination of free amino acids. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a method for determining the formation potential of nitrogen-containing disinfection by-products during the chlorination of amino acids, which has high precision, good repeatability, and is convenient for comparison and verification.

[0007] The technical solution of the present invention is as follows:

[0008] The present invention provides a method for determining the formation potential of nitrogen-containing disinfection by-products during the chlorination of amino acids, comprising the following steps:

[0009] S1: Use amino acids as TOC to form a sample solution and adjust the pH value of the sample solution;

[0010] S2: Add chlorine to determine the chlorine dosage and incubation time;

[0011] S3: Measure the concentration of nitrogen-containing disinfection by-products in the sample solution, and the nitrogen-containing disinfection by-products include haloacetonitrile, halonitromethane, and haloacetamide;

[0012] S4: Divide the measured concentration of the nitrogenous disinfection by-product by the concentration of the amino acid, and the resulting value is the corresponding formation potential of the nitrogenous disinfection by-product.

[0013] Among them, in the method for measuring the formation potential of haloacetonitrile, the chlorine dosage calculation formula for the chlorination reaction is: the residual chlorine remains at 1 ± 0.2 mg / L after 24 hours of chlorination reaction.

[0014] In the method for measuring the formation potential of halo-nitromethane, the chlorine dosage calculation formula for the chlorination reaction is: the residual chlorine remains at 1 ± 0.2 mg / L after 24 hours of chlorination reaction.

[0015] In the method for measuring the formation potential of haloacetamide, the chlorine dosage calculation formula for the chlorination reaction is: Cl (mg / L) = 3 × DOC.

[0016] Further, use 10 mM phosphate buffer to adjust the pH value of the sample solution.

[0017] Further, the pH value of the sample solution is 7.

[0018] Further, the incubation time in step S2 is 24 hours.

[0019] Further, it is necessary to incubate in the dark during the cultivation process.

[0020] Further, the sample solution also includes phosphate buffer, bromide and iodide. The concentration of the phosphate buffer is 10 mM, the concentration of the bromide is 200 μg / L, the concentration of the iodide is 20 μg / L, the concentration of the amino acid is 10 mg / L, and the chlorination reaction of the sample solution is carried out in a brown glass bottle.

[0021] Further, the amino acid is aspartic acid, alanine, glycine or serine.

[0022] Further, measuring the concentration of the nitrogenous disinfection by-product in the sample solution in step S3 includes the following steps:

[0023] S31: Based on the chlorine dosage calculation formula for the chlorination reaction in the method for measuring the formation potential of various nitrogenous disinfection by-products, after determining the chlorine dosage, carry out the chlorination reaction;

[0024] S32: After the reaction ends, quench the residual chlorine in the solution with ascorbic acid with a molar residual chlorine concentration of 120% to terminate the continuous reaction;

[0025] S33: Use the method of liquid-liquid extraction to obtain the extract of the nitrogenous disinfection by-product;

[0026] S4 analyzes the extract by GC-MS method.

[0027] Furthermore, the liquid-liquid extraction method includes:

[0028] Acidify the quenched sample with concentrated sulfuric acid, then add sodium sulfate and methyl tert-butyl ether, let it stand after reaction, and collect the organic layer;

[0029] Repeat the liquid-liquid extraction process again to obtain the extract;

[0030] Remove the moisture from the extract through a column containing sodium sulfate, concentrate it under nitrogen, and transfer it to a gas chromatography vial.

[0031] Furthermore, for GC-MS instrumental analysis, an Agilent 7890 gas chromatography-5977 mass spectrometry combined instrument and an HP-5MS column are used for internal standard quantification.

[0032] The beneficial technical effects of the present invention are:

[0033] The present invention discloses a method for determining the formation potential of nitrogen-containing disinfection by-products during the chlorination of amino acids. By determining the chlorine dose calculation formula for the chlorination reaction in the method for determining the formation potential of nitrogen-containing disinfection by-products, the formation potential of various nitrogen-containing disinfection by-products during the chlorination of free amino acids can be accurately evaluated. The present invention improves the accuracy of FP testing by optimizing the chlorine dosage, improves the repeatability and reliability of the determination results, and facilitates data comparison and verification between different laboratories. Through the method for determining the formation potential of nitrogen-containing disinfection by-products during the chlorination of amino acids of the present invention, it can provide clear guidance for optimizing the chlorine dosage in the actual water treatment process, help reduce the generation of N-DBPs, effectively reduce the content of these harmful substances in drinking water, and thus improve the safety of water quality. Brief Description of the Drawings

[0034] Figure 1 is a flow chart of the method for determining the formation potential of nitrogen-containing disinfection by-products in line with the present invention;

[0035] Figure 2 is a bar chart of the formation potential of nitrogen-containing disinfection by-products under the best model in line with the present invention. Detailed Embodiments

[0036] In order to be able to more clearly understand the technical means of the present invention and implement it according to the content of the specification, the following combines the drawings and embodiments to further describe in detail the specific embodiments of the present invention. The following embodiments are used to illustrate the present invention but not to limit the scope of the present invention.

[0037] Please refer to Figure 1 as shown, the present invention provides a method for determining the formation potential of nitrogen-containing disinfection by-products during the chlorination of amino acids, and according to Figure 1The nitrogenous disinfection by-product formation potential under the optimal model during the chlorination of different amino acids was calculated by the measurement method shown below, see Figure 2 .

[0038] Please continue to refer to Figure 1 and Figure 2 As shown, a method for measuring the nitrogenous disinfection by-product formation potential during the chlorination of an amino acid includes the following steps:

[0039] S1: Using the amino acid as the TOC, a sample solution is formed, and the pH value of the sample solution is adjusted. The amino acid is aspartic acid (Asp), alanine (Ala), glycine (Gly), or serine (Ser). The pH value of the sample solution is adjusted using a 10 mM phosphate buffer so that the pH value of the sample solution is 7. The sample solution also includes a phosphate buffer, bromide, and iodide. The concentration of the phosphate buffer is 10 mM, the concentration of the bromide is 200 μg / L, the concentration of the iodide is 20 μg / L, and the concentration of the amino acid is 10 mg / L.

[0040] S2: Chlorine is added to determine the chlorine dosage and the incubation time. Optionally, the incubation time is 24 hours, and during the incubation process, it is necessary to incubate in the dark. Therefore, the chlorination reaction of the sample solution is carried out in a brown glass bottle.

[0041] S3: Measure the concentration of nitrogenous disinfection by-products in the sample solution. The nitrogenous disinfection by-products include haloacetonitrile, halonitromethane, and haloacetamide;

[0042] Further, measuring the concentration of nitrogenous disinfection by-products in the sample solution in step S3 includes the following steps:

[0043] S31: Based on the chlorine dosage calculation formula for the chlorination reaction in the measurement method of the formation potential of the concentration of various nitrogenous disinfection by-products, after determining the chlorine dosage, the chlorination reaction is carried out;

[0044] S32: After the reaction ends, ascorbic acid with a 120% molar residual chlorine concentration is used to quench the residual chlorine in the solution to terminate the continuous reaction;

[0045] S33: The liquid-liquid extraction method is used to obtain the extract of the nitrogenous disinfection by-products.

[0046] Further, the liquid-liquid extraction method includes:

[0047] The quenched sample is acidified with concentrated sulfuric acid, then sodium sulfate and methyl tert-butyl ether are added, and after the reaction, it is left to stand, and the organic layer is collected;

[0048] The liquid-liquid extraction process is repeated again to obtain the extract;

[0049] The extract is passed through a column containing sodium sulfate to remove moisture, concentrated under nitrogen, and transferred to a gas chromatography vial.

[0050] S34: Analyze the extract by GC-MS method. Further, for the GC-MS instrumental analysis, an Agilent 7890 gas chromatography - 5977 mass spectrometry combined instrument and an HP-5MS column are used for internal standard quantification.

[0051] S4: Divide the concentration of the nitrogen-containing disinfection by-product measured / the concentration of the amino acid, and the resulting value is the formation potential of the corresponding nitrogen-containing disinfection by-product.

[0052] Among them, in the determination method of the formation potential of haloacetonitrile, the calculation formula for the chlorine dosage in the chlorination reaction is: the residual chlorine remains at 1 ± 0.2 mg / L after 24 h of chlorination reaction;

[0053] In the determination method of the formation potential of halonitromethane, the calculation formula for the chlorine dosage in the chlorination reaction is: the residual chlorine remains at 1 ± 0.2 mg / L after 24 h of chlorination reaction;

[0054] In the determination method of the formation potential of haloacetamide, the calculation formula for the chlorine dosage in the chlorination reaction is: Cl (mg / L) = 3 × DOC.

[0055] By determining the calculation formula for the chlorine dosage in the chlorination reaction in the determination method of the formation potential of nitrogen-containing disinfection by-products, the present invention can accurately evaluate the formation potential of various nitrogen-containing disinfection by-products during the chlorination of free amino acids. Moreover, the repeatability and reliability of the measurement results facilitate data comparison and verification between different laboratories. Through the method for determining the formation potential of nitrogen-containing disinfection by-products during the chlorination of amino acids of the present invention, it can provide clear guidance for optimizing the chlorine dosage in the actual water treatment process, help reduce the generation of N-DBPs, effectively reduce the content of these harmful substances in drinking water, and thus improve the safety of water quality.

[0056] Example 1

[0057] For haloacetonitrile (HANs), the best FP determination method should be that the residual chlorine remains at 1 ± 0.2 mg / L after 24 h of chlorination reaction. That is, in Example 1, the chlorine dosage is such that the residual chlorine remains at 1 ± 0.2 mg / L after 24 h of chlorination reaction.

[0058] Specifically, prepare four sample solutions, and add one kind of amino acid to each sample solution.

[0059] Take a 125 mL brown glass bottle, add 10 mM phosphate buffer (pH = 7), 200 μg / L bromide, 20 μg / L iodide, and 10 mg / L amino acid as TOC and chlorine. Incubate in the dark in an incubator at 25 °C for 24 h.

[0060] Quenching residual chlorine: After the reaction, ascorbic acid with a molar concentration of 120% of the residual chlorine was used to quench the residual chlorine in the solution to terminate the continuous reaction.

[0061] Liquid-liquid extraction: In a 125 mL brown bottle, the quenched sample of 100 mL was acidified with concentrated sulfuric acid (pH < 1). Then 15 g of sodium sulfate and 8 mL of methyl tert-butyl ether (MTBE) were added, shaken by hand for 1 minute, and left to stand for 1 minute. The organic layer was collected and transferred into a 20 mL glass test tube. The liquid-liquid extraction procedure was repeated again. The obtained extract was passed through a column containing 3 g of sodium sulfate to remove moisture, concentrated to 200 μL under nitrogen, and transferred to a 2 mL gas chromatography vial. 10 μL of 1,2-dibromopropane internal standard (25 mg / L) was added for GC-MS instrument analysis.

[0062] Instrument analysis: The instrument analysis of the sample was carried out using an Agilent 7890 gas chromatography-5977 mass spectrometer and an HP-5MS column for internal standard quantification.

[0063] The specific parameters are as follows: The chromatographic column is an HP-5ms chromatographic column, model 30 m x 0.25 mm x 0.25 μm. The carrier gas is ultra-high purity helium (purity greater than 99.999%), and the helium carrier gas is a constant flow rate (1.2 mL / min). The inlet temperature is 220 °C. Injection mode: Split injection was used, the injection volume was 1 μL, and the split ratio was 5:1. The temperature program was: maintained at an initial temperature of 35 °C for 2 min, then heated at a rate of 4 °C / min to 100 °C and held for 2 min, then heated at a rate of 9 °C / min to 130 °C and held for 1 min, and finally heated at a rate of 12 °C / min to 220 °C and held for 1 min. The ion source temperature and quadrupole temperature are 230 °C and 150 °C respectively, and the electron energy is 70 eV. Sample analysis was carried out in selected ion monitoring (SIM) mode.

[0064] The formation potential (FP) of haloacetonitriles in four amino acids is shown in Table 1.

[0065] Table 1 Formation potential (FP) of haloacetonitriles (HANs) (μg / mg)

[0066]

[0067]

[0068] As can be seen from Table 1, when the chlorine dosage is such that the residual chlorine remains at 1 ± 0.2 mg / L after 24 h of chlorination reaction, the formation potentials of haloacetonitriles in the four amino acids are 103.53 μg / mg, 0.13 μg / mg, 0.02 μg / mg, and 0.01 μg / mg respectively. That is, during the chlorination process, aspartic acid (Asp) mainly produces dichloroacetonitrile (DCAN) and bromochloroacetonitrile (BCAN), with formation potentials of 80.63 μg / mg and 21.94 μg / mg respectively. This indicates that aspartic acid is the main precursor of haloacetonitriles during the chlorination process, especially with a relatively high concentration of DCAN being produced. The formation potential of alanine is relatively low, mainly producing a small amount of DCAN (0.06 μg / mg) and BCAN (0.04 μg / mg). The formation potential of glycine is even lower, with only a small amount being produced in BCAN (0.01 μg / mg), and the formation potentials of other haloacetonitriles are almost zero. The formation potential of serine is the lowest, with only an extremely small amount being produced in BCAN (0.01 μg / mg), and the formation potentials of other haloacetonitriles are almost zero.

[0069] It can be seen therefrom that aspartic acid is the main precursor of haloacetonitriles, and reducing the content of aspartic acid in water can effectively reduce the formation of haloacetonitriles.

[0070] Comparative Examples 1 - 4

[0071] In Comparative Examples 1, 2, 3, and 4, the chlorine dosages are respectively Cl (mg / L) = 3×DOC + 8×NH3–N + 10, Cl (mM) = 10×M, Cl (mM) = 15×M, Cl (mg / L) = 3×DOC. Wherein, M is the molar mass of the amino acid. Other steps are carried out for experiments and detections according to the method of Example 1, and the results are shown in Table 2.

[0072] Table 2 Formation Potentials of Haloacetonitriles (μg / mg) of Typical Amino Acids at Different Chlorine Dosages

[0073]

[0074]

[0075] As can be seen from Table 2, for Asp, the total formation potentials of haloacetonitriles (sum of 7 HANs) at different chlorine dosages are 37.2, 18.3, 5.5, 53.3, and 104 μg / mg respectively. Thus, it can be seen that in Example 1, when the chlorine dosage is such that the residual chlorine remains at 1 ± 0.2 mg / L after 24 h of chlorination reaction, the formation potential of haloacetonitriles is the highest.

[0076] For Ala, the total potential for the formation of haloacetonitriles at different chlorine dosages (the sum of 7 HANs) was 1.5, 0.2, 0.1, 0.1, and 0.1 μg / mg, respectively. That is, in Comparative Example 1, when the chlorine dosage was Cl (mg / L) = 3×DOC + 8×NH3–N + 10, the potential for the formation of haloacetonitriles was the highest.

[0077] The total potential for the formation of haloacetonitriles (the sum of 7 HANs) of Gly and Ser was less than 0.1 μg / mg in all models, so their data was ignored.

[0078] Since the concentration of Asp in drinking water is higher than that of Ala, the impact of Asp on the potential for the formation of haloacetonitriles will be much higher than that of Ala. Therefore, the best method for determining the potential for the formation of haloacetonitriles should be to maintain the residual chlorine at 1 ± 0.2 mg / L after 24 h of chlorination reaction.

[0079] Example 2

[0080] For halo-nitromethanes (HNMs), the best method for determining the FP should be to maintain the residual chlorine at 1 ± 0.2 mg / L after 24 h of chlorination reaction. That is, in Example 2, the chlorine dosage was to maintain the residual chlorine at 1 ± 0.2 mg / L after 24 h of chlorination reaction.

[0081] The experiment and detection were carried out according to the method of Example 1, and the results are shown in Table 3.

[0082] Table 3 Formation potential (FP) of halo-nitromethanes (HNMs) (μg / mg)

[0083]

[0084] As can be seen from Table 3, when the chlorine dosage was to maintain the residual chlorine at 1 ± 0.2 mg / L after 24 h of chlorination reaction, the formation potentials of halo-nitromethanes in the four amino acids were 0.07 μg / mg, 0.42 μg / mg, 0.38 μg / mg, and 0.01 μg / mg, respectively. That is, for halo-nitromethanes, the formation potential of alanine (Ala) was relatively high, mainly generating BNM (0.02 μg / mg) and BCNM (0.4 μg / mg), with a total of 0.42 μg / mg. This indicates that alanine is an important precursor of halo-nitromethanes during the chlorination process. The formation potential of glycine (Gly) was medium, mainly generating BCNM (0.36 μg / mg), with a total of 0.38 μg / mg. This indicates that glycine can also generate a certain amount of halo-nitromethanes during the chlorination process. The formation potentials of aspartic acid (Asp) and serine (Ser) were relatively low, indicating that their ability to generate halo-nitromethanes during the chlorination process was weak. Therefore, reducing the concentrations of alanine and glycine can effectively control the formation of halo-nitromethanes and reduce the impact of disinfection by-products on water quality.

[0085] Comparative Examples 5 - 8

[0086] Similarly, the chlorine dosages in Comparative Example 5, Comparative Example 6, Comparative Example 7, and Comparative Example 8 are Cl (mg / L) = 3×DOC + 8×NH3–N + 10, Cl (mM) = 10×M, Cl (mM) = 15×M, and Cl (mg / L) = 3×DOC, respectively. Here, M is the molar mass of the amino acid. Other steps are carried out for experiments and detections according to the method of Example 1, and the results are shown in Table 4.

[0087] Table 4 Formation potential of halo - nitro - methanes (μg / mg) of typical amino acids under different chlorine dosages

[0088]

[0089] As can be seen from Table 4, for Ala, the total formation potential of halo - nitro - methanes (the sum of 4 HNMs) under different chlorine dosages are 0.2 μg / mg, 0.2 μg / mg, 0.2 μg / mg, 0.3 μg / mg, and 0.4 μg / mg, respectively. For Gly, the total formation potential of halo - nitro - methanes (the sum of 4 HNMs) under different chlorine dosages are 0 μg / mg, 0 μg / mg, 0.1 μg / mg, 0 μg / mg, and 0.4 μg / mg, respectively.

[0090] Since alanine and glycine are the main precursors for the formation of halo - nitro - methanes, therefore, the best way to determine the formation potential of halo - nitro - methanes should be that the residual chlorine remains at 1 ± 0.2 mg / L after 24 - hour chlorination reaction.

[0091] Example 3

[0092] For halo - acetamides (HAMs), the calculation formula for the optimal chlorine dose in the chlorination reaction is: Cl (mg / L) = 3×DOC. That is, in Example 3, the chlorine dosage is Cl (mg / L) = 3×DOC. Other steps are carried out for experiments and detections according to the method of Example 1, and the results are shown in Table 5.

[0093] Table 5 Formation potential (FP) of halo - acetamides (HAMs) (μg / mg)

[0094]

[0095] As can be seen from Table 5, when the chlorine dosage is Cl (mg / L) = 3×DOC, the formation potentials of haloacetamides in the four amino acids are 173.39 μg / mg, 0.1 μg / mg, 0.06 μg / mg, and 0.06 μg / mg respectively. That is, for haloacetamides, the formation potential of aspartic acid (Asp) is the highest, mainly producing DCAM (148.46 μg / mg), with a total of 173.39 μg / mg. This indicates that aspartic acid is the main precursor of haloacetamides. The lower formation potentials of other amino acids (alanine, glycine, serine) indicate that their ability to form haloacetamides during chlorination is weak. Therefore, reducing the concentration of aspartic acid can effectively control the formation of haloacetamides and reduce the impact of disinfection by-products on water quality.

[0096] Comparative Examples 9 - 12

[0097] Similarly, the chlorine dosages in Comparative Example 9, Comparative Example 10, Comparative Example 11, and Comparative Example 12 are Cl (mg / L) = 3×DOC + 8×NH3–N + 10, Cl (mM) = 10×M, Cl (mM) = 15×M, and the residual chlorine remains at 1 mg / L after 24 h of chlorination reaction. Among them, M is the molar mass of the amino acid. Other steps are carried out for experiments and detections according to the method of Example 1, and the results are shown in Table 6.

[0098] Table 6 Formation Potentials of Haloacetamides of Typical Amino Acids under Different Chlorine Dosages (μg / mg)

[0099]

[0100]

[0101] As can be seen from Table 6, for Asp, the total formation potentials of halonitromethanes under different chlorine dosages (the sum of 4 HNMs) are 46.6 μg / mg, 21.1 μg / mg, 6.5 μg / mg, 132 μg / mg, and 173 μg / mg respectively. Since aspartic acid is the main precursor of haloacetamides, therefore, the best way to determine the formation potential of haloacetamides is that the best chlorine dosage calculation formula for chlorination reaction is: Cl (mg / L) = 3×DOC.

[0102] In summary, a method for determining the formation potential of nitrogenous disinfection by-products during amino acid chlorination is disclosed. By determining the chlorine dosage calculation formula for the chlorination reaction in the method for determining the formation potential of nitrogenous disinfection by-products, the formation potential of various nitrogenous disinfection by-products during free amino acid chlorination can be accurately evaluated. The present invention improves the accuracy of FP testing by optimizing the chlorine dosage, enhances the repeatability and reliability of the determination results, and facilitates data comparison and verification between different laboratories. Through the method for determining the formation potential of nitrogenous disinfection by-products during amino acid chlorination of the present invention, it is possible to provide clear guidance for optimizing the chlorine dosage in the actual water treatment process, contribute to reducing the formation of N-DBPs, effectively reduce the content of these harmful substances in drinking water, and thus improve the safety of water quality.

[0103] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process, characterized in that: The following steps are involved: S1: Using amino acids as TOC to form a sample solution and adjusting the pH value of the sample solution; S2: adding chlorine, determining the chlorine dosage and incubation time; S3: Determine the concentration of nitrogen-containing disinfection by-products in the sample solution, wherein the nitrogen-containing disinfection by-products include halogenated acetonitrile, halogenated nitromethane and halogenated acetamide; S4: measuring the concentration of the nitrogen-containing disinfection by-product / the concentration of the amino acid, and the result obtained is the corresponding nitrogen-containing disinfection by-product generation potential; Among them, the calculation formula of the chlorine dosage of the chlorination reaction in the determination method of the formation potential of halogenated acetonitrile is: the residual chlorine is maintained at 1±0.2mg / L after 24h of chlorination reaction; The formula for calculating the chlorine dosage for the chlorination reaction in the determination method for determining the formation potential of halonitromethanes is: the residual chlorine remains at 1±0.2 mg / L after 24 h of chlorination reaction; The chlorine dosage calculation formula for the chlorination reaction in the determination method for determining the formation potential of haloacetamide is: Cl (mg / L) = 3×DOC.

2. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 1, characterized in that: The pH value of the sample solution was adjusted using 10 mM phosphate buffer.

3. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 2, characterized in that: The pH value of the sample solution is 7.

4. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 1, characterized in that: The culture time in step S2 is 24 hours.

5. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 4, characterized in that: The culture needs to be kept away from light during incubation.

6. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 1, characterized in that: The sample solution also includes phosphate buffer, bromide and iodide, the concentration of the phosphate buffer is 10mM, the concentration of the bromide is 200μg / L, the concentration of the iodide is 20μg / L, the concentration of the amino acid is 10mg / L, and the chlorination reaction of the sample solution is carried out in a brown glass bottle.

7. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 1, characterized in that: The amino acid is aspartic acid, alanine, glycine or serine.

8. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 1, characterized in that: Determining the concentration of nitrogen-containing disinfection byproducts in the sample solution in step S3 comprises the following steps: S31: Based on the chlorine dosage calculation formula of the chlorination reaction in the determination method of the concentration generation potential of various nitrogen-containing disinfection by-products, after determining the chlorine dosage, the chlorination reaction is carried out; S32: After the reaction is completed, ascorbic acid with a molar residual chlorine concentration of 120% is used to quench the residual chlorine in the solution to terminate the reaction; S33: obtaining an extract of nitrogen-containing disinfection by-products by liquid-liquid extraction; S34: Analyze the extract using GC-MS method.

9. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 8, characterized in that: The liquid-liquid extraction method comprises: The quenched sample was acidified with concentrated sulfuric acid, and then sodium sulfate and methyl tert-butyl ether were added. After the reaction, the sample was allowed to stand and the organic layer was collected. Repeat the liquid-liquid extraction process again to obtain an extract; The extract was passed through a column containing sodium sulfate to remove moisture, concentrated to 50 Å under nitrogen, and transferred to a gas chromatography bottle.

10. The method for determining the potential for formation of nitrogen-containing disinfection by-products in the amino acid chlorination process according to claim 9, characterized in that: GC-MS instrumental analysis used an Agilent 7890 gas chromatograph-5977 mass spectrometer and an HP-5MS column for internal standard quantification.

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