A method for analyzing the material transformation of extracellular polymers during UV / peracetic acid disinfection at the molecular level

Abstract

The present invention relates to a method for analyzing the material transformation of extracellular polymers during ultraviolet / peracetic acid disinfection at a molecular level, which belongs to the technical field of sewage treatment, and comprises the following steps: step S1. adding peracetic acid to water containing extracellular polymers, and then stirring evenly to obtain a mixed liquid; step S2. subjecting the mixed liquid obtained in step S1 to ultraviolet irradiation to obtain various graded components; step S3. performing a systematic analysis on the various graded components obtained in step S2. The method for analyzing the material transformation of extracellular polymers during ultraviolet / peracetic acid disinfection at a molecular level of the present invention is suitable for analyzing the material transformation of extracellular polymers under ultraviolet / peracetic acid treatment from a molecular level, and the peracetic acid used is widely available and inexpensive, and can be used for sewage treatment to effectively reduce costs; due to the short reaction time, the ultraviolet dose used in the process is low, so the construction cost and operation cost are low.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method for analyzing the material transformation of extracellular polymers during ultraviolet / peracetic acid disinfection at a molecular level. Background Art

[0002] In recent years, with the development of water treatment technology and the acceleration of urbanization, the demand for clean water has continued to increase. In addition, the emergence of a variety of emerging pollutants has also brought huge challenges to water safety. As one of the most important water treatment processes, water disinfection can effectively remove pollutants and inactivate pathogens, and can also have a certain removal effect on various emerging pollutants. This is an important guarantee for environmental safety and public health.

[0003] Ultraviolet (UV) disinfection and chlorine disinfection are the most common traditional disinfection processes in the disinfection of sewage and drinking water. Although these processes can achieve the inactivation of pathogens, they also have many problems such as pathogen regeneration and excessive by-products. In recent years, peracetic acid has gradually attracted attention as a strong disinfectant with a wide range of effects and strong effects. In addition, the UV-based advanced oxidation process (UV-AOP) has been widely studied due to its good disinfection effect and less by-product generation; UV-AOP can not only inactivate conventional pathogens, but also show a high removal effect on emerging pollutants; the technology of combining UV with peracetic acid has attracted extensive research. This process can produce highly reactive free radicals, thereby efficiently removing pathogens and micropollutants, and can also reduce the possibility of forming disinfection by-products (DBP). Therefore, it is necessary to comprehensively analyze the mechanism of pathogen inactivation by the UV / peracetic acid combined disinfection process.

[0004] Extracellular polymers (EPS) are a type of high molecular weight biopolymer that wraps around the surface of pathogens. They are not only a barrier for pathogens to resist adverse environments, but also a place for biochemical reactions to occur, and an important interface for pathogens to communicate with the external environment and exchange substances. The impact of EPS on the disinfection process can be divided into two parts. On the one hand, EPS can form a molecular layer outside the cell, thereby preventing some active substances, such as reactive oxygen, reactive chlorine and other disinfectants from entering the cell. On the other hand, once the bacteria are inactivated, their stress protection mechanism will be triggered, thereby producing more EPS. In addition, EPS is also an important interface for the removal of exogenous organic matter. It contains many enzyme systems and has redox and photoreaction capabilities, which makes it show a highly correlated biochemical effect on exogenous organic matter. However, there is currently no method that can fully analyze the material transformation of extracellular polymers during UV / peracetic acid disinfection at the molecular level. Summary of the invention

[0005] The object of the present invention is to provide a method for analyzing the material transformation of extracellular polymers in the process of ultraviolet / peracetic acid disinfection at the molecular level to solve the above-mentioned problems in the prior art. The method of the present invention uses an ultrasonic-thermal extraction method to grade the extracellular polymers of different forms in the secondary effluent of an actual sewage treatment plant (soluble extracellular polymers (S-EPS), loosely bound extracellular polymers (LB-EPS) and tightly bound extracellular polymers (TB-EPS)), add 10 mg / L peracetic acid solution to the extracted extracellular polymer solution, and perform ultraviolet irradiation (the radiation dose of ultraviolet light is 108 mJ / cm 2 ), analyze the material transformation of different forms of extracellular polymers from the analytical level; first, through total organic carbon and UV 254 The indicators preliminarily determined the overall degradation of extracellular polymers during UV / peracetic acid disinfection; further, a three-component model of extracellular polymers was constructed through three-dimensional fluorescence-parallel factor analysis to analyze the changes in fluorescence response of extracellular polymers; finally, Fourier transform ion cyclotron resonance mass spectrometry was used to analyze the changes in element clustering, material composition and molecular formula of different forms of extracellular polymers before and after UV / peracetic acid disinfection. The results showed that the different C, H, O and N components of the three forms of extracellular polymers before and after the reaction also had different changes, and the overall distribution was in the direction of high O:C; in addition, through the division and analysis of seven components including lipids, proteins, carbohydrates, unsaturated hydrocarbons, lignin, tannins and condensed aromatic structures, it was found that the newly generated molecular formulas of the three forms of extracellular polymers all had higher O:C and H:C, while the disappeared molecular formulas were concentrated in the low O:C region. This result also shows that UV / peracetic acid disinfection mainly degrades aromatic compounds with low oxidation degree and high molecular weight, converting them into low molecular weight compounds with high oxidation degree and saturation.

[0006] The comprehensive evaluation method used in the present invention can accurately analyze the material change rules of extracellular polymers during ultraviolet / peracetic acid disinfection at the molecular level, providing a scientific basis for proposing measures to reduce the barrier effect of extracellular polymers during the disinfection process.

[0007] To achieve the above object, the present invention provides a method for analyzing the material transformation of extracellular polymers during ultraviolet / peracetic acid disinfection at a molecular level, which comprises the following steps:

[0008] Step S1. adding peracetic acid to water containing extracellular polymers, and then stirring evenly to obtain a mixed liquid;

[0009] Step S2. subjecting the mixed liquid obtained in step S1 to ultraviolet irradiation to obtain various graded components;

[0010] Step S3: Perform a systematic analysis on the graded components obtained in step S2.

[0011] Preferably, in the method, the concentration of peracetic acid in step S1 is 10 mg / L, the stirring speed is 100 rpm, and the stirring time is 2 min.

[0012] Preferably, in the method, the radiation dose of ultraviolet irradiation in step S2 is 108 mJ / cm 2 .

[0013] Preferably, in the method described above, the system analysis in step S3 includes ultraviolet analysis, three-dimensional fluorescence-parallel factor analysis, and Fourier transform ion cyclotron resonance mass spectrometry analysis to comprehensively characterize each graded component.

[0014] Preferably, the method, wherein the UV analysis of total organic carbon and UV 254 The three-dimensional fluorescence-parallel factor analysis specifically includes the following steps:

[0015] Step S31. Take the sample to be tested and put it into a cuvette, then put the cuvette into the sample chamber of the spectrometer, set the scanning speed, excitation wavelength and emission wavelength of the spectrometer, and then start the test;

[0016] Step S32. Use parallel factor analysis to model and fit the test data to find the optimal number of components;

[0017] Step S33. Use the component numbers fitted in step S32 to compare the specific changes of different components after being treated with UV / peracetic acid.

[0018] When using three-dimensional fluorescence-parallel factor analysis, it is necessary to compare and screen the modeling effects. The number of components in the system is determined by evaluating the residual sum of squares, and then the analysis is performed. The degradation effect of UV / peracetic acid on extracellular polymers is then judged based on the change in fluorescence response intensity before and after the reaction.

[0019] Preferably, the method, wherein the Fourier transform ion cyclotron resonance mass spectrometry analysis specifically comprises the following steps:

[0020] Step S41. Put the sample to be tested into a cuvette, and then put the cuvette into the sample chamber of the Fourier transform ion cyclotron resonance mass spectrometer, screen the element clustering by parameter setting to obtain the four main element compositions of CHO, CHON, CHONS and CHOS, and then analyze the element clustering, material composition and molecular formula of the extracellular polymers before and after UV / peracetic acid disinfection;

[0021] Step S42: Analyze the molecular formula by molecular formula matching, and then calculate the changes in the molecular properties of the extracellular polymers before and after UV / peracetic acid disinfection.

[0022] Preferably, in the method, step S42 further comprises the following steps:

[0023] Step S421. Perform molecular formula matching on the molecular formulas before and after UV / peracetic acid disinfection, use known CHO compounds in soluble organic matter for internal standard calibration, and perform molecular formula matching according to the following parameters after calibration: S / N>4, the number of elements is as follows, C 1-∝ ,H 1-∝ ,O 1-∝ ,N 0-3 ,S 0-1 , and obtain the possible molecular formula results;

[0024] Step S422. Further screen the possible molecular formula results of step S421, and retain the molecular formulas with 0.2<=H / C<=2.3 and 0<=O / C<=1.2;

[0025] Step S423. Retain the molecular formulas with DBE-O values ​​in the range of -10 to 10. If one m / z value corresponds to multiple possible molecular formulas, retain the molecular formula with the smallest number of heteroatoms. If there are still non-unique molecular formulas, retain the molecular formula with the smallest error value; the number of heteroatoms is the sum of N+S.

[0026] Step S424. Analyze the mass spectrum peaks with m / z values ​​ranging from 100-800 Da.

[0027] Preferably, in the method, the extracellular polymers in step S1 include soluble extracellular polymers, loosely bound extracellular polymers and tightly bound extracellular polymers, and the extracellular polymers are extracted from the secondary effluent of the sewage treatment plant by ultrasonic-thermal extraction, and the extraction method comprises the following steps:

[0028] Step a. providing a uniformly mixed sludge mixture, centrifuging the sludge mixture, and then filtering the supernatant with a filter membrane, and taking the filtrate as soluble extracellular polymers (S-EPS);

[0029] Step b. Add 0.01 mol / L sodium chloride solution to the sludge after centrifugation in step a to the original volume of the sludge mixture, sonicate, centrifuge, and then filter the supernatant with a filter membrane to obtain the filtrate, which is the loosely bound extracellular polymer (LB-EPS);

[0030] Step c. Remove the supernatant from step b, add 0.01 mol / L sodium chloride solution to the remaining sludge to the original volume of the sludge mixture, and place in a water bath at 70-90°C for 20 min-40 min, centrifuge, and then filter the supernatant through a filter membrane. The filtrate is the tightly bound extracellular polymer (TB-EPS).

[0031] Preferably, in the method, the centrifugation temperature in step a is 1-4°C, the centrifugation speed is 8000rpm-10000rpm, and the centrifugation time is 8-10min.

[0032] Preferably, in the method, the centrifugal speed in step b and step c is 10000rpm-12000rpm, the centrifugal time is 5min-15min, the ultrasonic time in step b is 4min-10min, and the ultrasonic frequency is 30kHZ-40kHZ.

[0033] After UV / peracetic acid treatment, the C, H, O, and N components of the extracellular polymers were distributed in the direction of high O: C. The main extracellular polymers degraded by UV / peracetic acid disinfection were aromatic compounds with low oxidation degree and high molecular weight, which were converted into low molecular weight compounds with high oxidation degree and saturation state.

[0034] Beneficial effects:

[0035] 1) The method for analyzing the material transformation of extracellular polymers during UV / peracetic acid disinfection at the molecular level of the present invention is suitable for analyzing the material transformation of extracellular polymers under UV / peracetic acid treatment at the molecular level. The peracetic acid used is widely available and inexpensive, and can be used for sewage treatment to effectively reduce costs. Due to the short reaction time and the low UV dose used in the process, the construction cost and operating cost are low.

[0036] 2) The method of the present invention for analyzing the transformation of extracellular polymers during UV / peracetic acid disinfection at the molecular level, using total organic carbon and UV 254 The results showed that after UV / peracetic acid treatment, different forms of extracellular polymers were degraded to varying degrees (47.4% to 70.5%). 254 The results further confirmed that the intensity of humus organic matter and aromatic compounds in extracellular polymers gradually decreased with the progress of UV / peracetic acid disinfection. Furthermore, combined with three-dimensional fluorescence characterization and parallel factor analysis, it was confirmed that the fluorescence response intensity of different forms of extracellular polymers was significantly reduced after UV / peracetic acid treatment and disinfection, among which the fluorescence response intensity of S-EPS and LB-EPS decreased by 29.05% and 37.71%, respectively.

[0037] 3) The method of the present invention for analyzing the material transformation of extracellular polymers during UV / peracetic acid disinfection at the molecular level, uses Fourier transform ion cyclotron resonance mass spectrometry to analyze the changes in molecular characteristics of extracellular polymers of different forms during UV / peracetic acid disinfection. The results show that the aromaticity of extracellular polymers of different forms is reduced after UV / peracetic acid disinfection, and small molecules with low aromaticity are generated. However, the degree of oxidation and saturation of the extracellular polymers are increased, which is mainly related to the oxidative effect of free radicals in the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The figure shows the changes in total organic carbon of three different forms of extracellular polymers during UV / peracetic acid disinfection.

[0039] Figure 2 Three different forms of extracellular polymers during UV / peracetic acid disinfection 254 Change graph.

[0040] Figure 3 Overall fluorescence response diagram of three different forms of extracellular polymers before (0 min) and after (60 min) UV / peracetic acid disinfection.

[0041] Figure 4 The results of modeling and fitting of the component changes of extracellular polymers during UV / peracetic acid disinfection using the parallel factor analysis method (mixed modeling of three forms of extracellular polymers) ((a) fluorescence emission wavelength variance, (b) fluorescence excitation wavelength variance).

[0042] Figure 5 Fluorescence response and fluorescence load results after division into three components ((a) fluorescence response of Component 1, (b) fluorescence load of Component 1, (c) fluorescence response of Component 2, (d) fluorescence load of Component 2, (e) fluorescence response of Component 3 and (f) fluorescence load of Component 3).

[0043] Figure 6 This is the result of Fourier transform ion cyclotron resonance mass spectrometry analysis of elements and substances in three different forms of extracellular polymers before and after UV / peracetic acid disinfection.

[0044] Figure 7Results of elemental clustering analysis of three different forms of extracellular polymers by Fourier transform ion cyclotron resonance mass spectrometry before and after UV / peracetic acid disinfection, as well as a graph showing changes in material composition (soluble extracellular polymers (a) and (d), loosely bound extracellular polymers (b) and (e), tightly bound extracellular polymers (c) and (f)) (material range—A: lipids, B: proteins, C: carbohydrates, D: unsaturated hydrocarbons, E: lignin, F: tannins, G: condensed aromatic structures).

[0045] Figure 8 The graph shows the results of Fourier transform ion cyclotron resonance mass spectrometry on the changes in the molecular formulas of three different forms of extracellular polymers before and after UV / peracetic acid disinfection ((a) soluble extracellular polymers, (b) loosely bound extracellular polymers and (c) tightly bound extracellular polymers). DETAILED DESCRIPTION

[0046] The present invention is described below by the best embodiment. It should be known to those skilled in the art that the embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0047] Example 1

[0048] A method for molecularly analyzing the material transformation of extracellular polymers during ultraviolet / peracetic acid disinfection, characterized in that it comprises the following steps:

[0049] Step S1. The extracellular polymer includes soluble extracellular polymer, loosely bound extracellular polymer and tightly bound extracellular polymer. 10 mg / L peracetic acid is added to water containing soluble extracellular polymer, loosely bound extracellular polymer and tightly bound extracellular polymer respectively, and then stirred to obtain three mixed liquids.

[0050] Step S2: The three mixed liquids obtained in step S1 are irradiated with a dose of 108 mJ / cm 2 Irradiating with ultraviolet light to obtain various graded components of each mixed liquid;

[0051] In step S1, the extracellular polymers are extracted from the secondary effluent of the sewage treatment plant by using an ultrasonic-thermal extraction method, and the extraction method comprises the following steps:

[0052] Step a. providing a uniformly mixed sludge mixture, centrifuging the sludge mixture at 8000 rpm for 8 min at 4°C, then filtering the supernatant with a 0.22 μm filter membrane, and taking the filtrate as the soluble extracellular polymer;

[0053] Step b. The sludge after centrifugation in step a is mixed with 0.01 mol / L sodium chloride solution to the original volume of the sludge mixture, ultrasonicated at 30 kHz for 4 min, centrifuged at 12000 rpm for 15 min, and then the supernatant is filtered with a 0.22 μm filter membrane, and the filtrate is the loosely bound extracellular polymer;

[0054] Step c. Remove the supernatant from the remaining sludge in step b, add 0.01 mol / L sodium chloride to the original volume of the sludge mixture, and place in a water bath at 80°C for 30 minutes, centrifuge at 12000 rpm for 5 minutes, and then filter the supernatant through a 0.22 μm filter membrane. The filtrate is the tightly bound extracellular polymer.

[0055] Example 2

[0056] The three mixed liquids of Example 1 were irradiated with a dose of 108 mJ / cm 2 The UV light was irradiated for different time periods, and then a certain amount of solution was taken out for total organic carbon and UV 254 The degradation effects of different forms of extracellular polymers were compared.

[0057] Each graded component is subjected to UV analysis, which includes the following steps:

[0058] (1) First, use a UV spectrophotometer to measure the UV 254 Indicators for testing;

[0059] (2) The sample was diluted with ultrapure water in proportion and sent to the total organic carbon detector to test the total organic carbon and analyze the UV 254 Indicators and total organic carbon results.

[0060] Example 3

[0061] The fractionated components obtained in Example 1 were subjected to three-dimensional fluorescence-parallel factor analysis, which specifically included the following steps:

[0062] Step S31. Take 3 mL of the sample to be tested and put it into a cuvette, wipe the transparent surface of the cuvette with mirror paper, and then put the cuvette into the sample chamber of the spectrometer (F-7100), the excitation light source is a xenon lamp, the scanning speed of the spectrometer is set to 12000 nm / min, the excitation wavelength is 200-600 nm, the interval is 10 nm, the emission wavelength is 200-600 nm, the interval is 10 nm, and then start the test;

[0063] Step S32: Use parallel factor analysis to model and fit the data. The three mixed liquids are irradiated with a dose of 108 mJ / cm 2The three-dimensional fluorescence data of 21 samples irradiated with ultraviolet light for 0, 5, 10, 15, 30, 45, and 60 minutes were summarized and then used for three-dimensional fluorescence modeling and fitting using parallel factor analysis. The corresponding component numbers and their corresponding characteristics were obtained through parallel factor analysis.

[0064] Step S33. Use the component numbers fitted in step S32 to compare the specific changes of different components after being treated with UV / peracetic acid.

[0065] Example 4

[0066] Three-dimensional fluorescence detection was performed on the three forms of extracellular polymer solutions at the initial time of 0 min and after 60 min of ultraviolet light irradiation, and the changes in the substances were preliminarily judged by comparing the fluorescence response characteristics before and after disinfection.

[0067] Example 5

[0068] The fractionated components obtained in Example 1 were subjected to Fourier transform ion cyclotron resonance mass spectrometry analysis, which specifically includes the following steps:

[0069] Step S41. Place the sample to be tested in a cuvette, and then place the cuvette in the sample chamber of the SolariX Fourier transform ion cyclotron resonance mass spectrometer of Bruker Company, screen the element clustering by parameter setting to obtain the four main element compositions of CHO, CHON, CHONS and CHOS, and then analyze the element clustering, material composition and molecular formula of the extracellular polymers before and after UV / peracetic acid disinfection. Each sample is 200 μL, and the injection mode is continuous injection;

[0070] Step S42. Analyze the molecular formula by molecular formula matching, and then calculate its change;

[0071] Step S42 further includes the following steps:

[0072] Step S421. Perform molecular formula matching on the molecular formulas before and after UV / peracetic acid disinfection, use known CHO compounds in soluble organic matter for internal standard calibration, and perform molecular formula matching according to the following parameters after calibration: S / N>4, the number of elements is as follows, C 1-∝ ,H 1-∝ ,O 1-∝ ,N 0-3 ,S 0-1 , and obtain the possible molecular formula results;

[0073] Step S422. Further screen the possible molecular formula results of step S421, and retain the molecular formulas with 0.2<=H / C<=2.3 and 0<=O / C<=1.2;

[0074] Step S423. Retain the molecular formulas with DBE-O values ​​in the range of -10 to 10. If one m / z value corresponds to multiple possible molecular formulas, retain the molecular formula with the smallest number of heteroatoms. If there are still non-unique molecular formulas, retain the molecular formula with the smallest error value; the number of heteroatoms is the sum of N+S.

[0075] Step S424. Analyze the mass spectrum peaks with m / z values ​​ranging from 100-800 Da.

[0076] Only the three forms of extracellular polymer solutions at the initial 0 min and after 60 min of reaction were taken for three-dimensional fluorescence detection, and the changes in the substances were preliminarily judged by comparing the fluorescence response characteristics before and after disinfection.

[0077] Example 6

[0078] Compared with Example 5, the difference is that the test performed is changed to Fourier transform ion cyclotron resonance mass spectrometry, and the analysis is for specific changes in the molecular formula.

[0079] The analysis results of Examples 2-6 are as follows Figure 1-8 , from the results we can conclude:

[0080] like Figure 1 As shown, Figure 1 The total organic carbon removal effect of Example 2 at different times is shown. Figure 1 It can be seen that after UV / peracetic acid disinfection, different forms of extracellular polymers were degraded to varying degrees (47.4%-70.5%), among which soluble extracellular polymers were degraded the most, reaching 70.5%, while tightly bound extracellular polymers were degraded the least, only 47.4%.

[0081] Figure 2 The UV spectra of three different forms of extracellular polymers in Example 2 are shown. 254 The removal effect, Figure 2 The results showed that after UV / peracetic acid disinfection, the concentrations of humic organic matter and aromatic compounds in different forms of extracellular polymers gradually decreased as the disinfection progressed.

[0082] The results of three-dimensional fluorescence analysis, such as Figure 3 , Figure 4 and Figure 5 As shown, Figure 3The changes in the overall fluorescence response intensity were shown. After UV / peracetic acid disinfection, the fluorescence intensity of the three different forms of extracellular polymers decreased to varying degrees, among which the attenuation of soluble extracellular polymers and loosely bound extracellular polymers was the strongest, with the peak intensity decreasing by 29.05% and 37.71%, respectively. Subsequently, the parallel factor analysis method was used to analyze the validity of the fluorescence spectrum data. After eliminating discrete values ​​with large deviations, parallel factor analysis models of 2 components, 3 components, and 4 components were constructed to quantitatively identify the fluorescence components. The mixed modeling results of the three forms of extracellular polymers are shown in Figure 2. Figure 4 As shown, it can be seen that compared with 2 components, 3 components and 4 components have obvious improvements, but compared with 3 components and 4 components, the residual sum of squares is close, and there is almost no obvious improvement. Therefore, 3 components are sufficient to meet the requirements of data analysis. Further, the fluorescence spectra and loadings of 3 components are analyzed. Figure 5 The results showed that C1 had fluorescence peaks at 240, 240 / 436nm excitation / emission wavelengths, which were mainly fulvic acid-like and humus-like substances, and were a ubiquitous natural organic compound; C2 had emission wavelength peaks at 200-250 and 280-400 and excitation wavelength peaks at 300-450, which were mainly protein-like substances; C3 had three response peaks, which were simple protein-like substances such as tryptophan and substances related to microbial by-products.

[0083] Fourier transform ion cyclotron resonance mass spectrometry data analysis results, such as Figure 6 , Figure 7 and Figure 8 As shown, Figure 6 and Figure 7 The results of elemental and material analysis of three different forms of extracellular polymers by Fourier transform ion cyclotron resonance mass spectrometry before and after UV / peracetic acid disinfection are shown. Figure 6 It shows that the elemental components of the three forms of extracellular polymers are not quite the same, but the overall trend is consistent, that is, the CHO and CHON components are higher than CHONS and CHOS; Figure 7It reflects the changes of components before and after disinfection in more detail, among which the CHO and CHON components of S-EPS increased by 4% and 6%, respectively, while the CHONS and CHOS components decreased by 6% and 4%, which indicates that the S-containing components are more easily attacked by the active groups generated in the UV / peracetic acid system, and after the reaction, they all move towards the high O / C area, indicating that the unsaturated substances containing S in the S-EPS components are consumed, and the generated substances are more saturated, which is also the case in the CHON component; in addition, the CHO component moves towards the low O / C direction, which indicates that this component consumes more oxygen-containing functional groups during the reaction, thereby producing many unsaturated substances that are easy to react; in LB-EPS The CHO and CHOS components increased by 3% and 6%, while the CHON and CHONS components decreased, which shows that the latter two components in LB-EPS have higher reactivity and are easily degraded; the Van diagram shows that both components are moving towards the direction of low H / C and high O / C, which indicates that the aromaticity of the two components decreases and the saturation increases after the reaction; the CHO and CHON components in TB-EPS increase slightly, but the CHONS and CHOS components decrease a lot, which shows that the latter two are the more reactive components in TB-EPS. It can be seen from the distribution of the Van diagram that the aromaticity of the CHO and CHON components decreases a lot after the reaction, while the saturation increases.

[0084] Figure 8 The results of Fourier transform ion cyclotron resonance mass spectrometry on the changes in molecular formulas of three different forms of extracellular polymers before and after UV / peracetic acid disinfection; the results show that the newly generated molecular formulas of the three forms of extracellular polymers have higher O:C and H:C, while the disappeared molecular formulas are concentrated in the low O:C region; this result also confirms that UV / peracetic acid disinfection mainly degrades aromatic compounds with low oxidation degree and high molecular weight, converting them into low molecular weight compounds with high oxidation degree and saturation; it is worth noting that among the three forms of extracellular polymers, the tightly bound extracellular polymers (TB-EPS) change the most, and more than 80% of the generated molecular formulas are concentrated in the high O:C and high H:C regions, indicating that the conversion products of TB-EPS after UV / peracetic acid disinfection have higher saturation and oxidation degree than the other two forms of EPS.

[0085] Compared with the prior art, the above embodiments have the following beneficial effects:

[0086] The present invention develops a comprehensive evaluation method for analyzing the material transformation of extracellular polymers during UV / peracetic acid disinfection at the molecular level, using total organic carbon and UV 254The results showed that after UV / peracetic acid treatment, different forms of extracellular polymers were degraded to varying degrees, with degradation rates ranging from 47.4% to 70.5%. 254 The results further confirmed that the intensity of humus organic matter and aromatic compounds in extracellular polymers gradually decreased with the progress of UV / peracetic acid disinfection process; further, combined with three-dimensional fluorescence characterization and parallel factor analysis, it was confirmed that the fluorescence response intensity of extracellular polymers of different forms was significantly reduced after UV / peracetic acid treatment and disinfection, among which the fluorescence response intensity of soluble extracellular polymers (S-EPS) and loosely bound extracellular polymers (LB-EPS) decreased by 29.05% and 37.71%, respectively. On this basis, the present invention further used Fourier transform ion cyclotron resonance mass spectrometry to analyze the changes in molecular properties of extracellular polymers of different forms during UV / peracetic acid disinfection. The results showed that the aromaticity of extracellular polymers of different forms was reduced after UV / peracetic acid disinfection, and small molecules with low aromaticity were generated. However, the degree of oxidation and saturation of extracellular polymers were increased, which was mainly related to the oxidation of free radicals in the system.

[0087] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for molecularly analyzing the material transformation of extracellular polymers during UV / peracetic acid disinfection, characterized in that: The following steps are involved: Step S1. adding peracetic acid to water containing extracellular polymers, and then stirring evenly to obtain a mixed liquid; Step S2. subjecting the mixed liquid obtained in step S1 to ultraviolet irradiation to obtain various graded components; Step S3. Performing a systematic analysis on the graded components obtained in step S2; The system analysis in step S3 includes ultraviolet analysis, three-dimensional fluorescence-parallel factor analysis, and Fourier transform ion cyclotron resonance mass spectrometry analysis to comprehensively characterize each graded component; UV analysis of total organic carbon and UV 254 The three-dimensional fluorescence-parallel factor analysis specifically includes the following steps: Step S31. Take the sample to be tested and put it into a cuvette, then put the cuvette into the sample chamber of the spectrometer, set the scanning speed, excitation wavelength and emission wavelength of the spectrometer, and then start the test; Step S32. Use parallel factor analysis to model and fit the test data to find the optimal number of components; Step S33. Using the component numbers fitted in step S32 to compare the specific changes of different components after UV / peracetic acid treatment; Fourier transform ion cyclotron resonance mass spectrometry analysis specifically includes the following steps: Step S41. Put the sample to be tested into a cuvette, and then put the cuvette into the sample chamber of the Fourier transform ion cyclotron resonance mass spectrometer, screen the element clusters by parameter setting to obtain the four main element compositions of CHO, CHON, CHONS and CHOS, and then analyze the element clusters, material composition and molecular formula of the extracellular polymers before and after UV / peracetic acid disinfection; Step S42. Analyze the molecular formula by molecular formula matching, and then calculate the changes in the molecular characteristics of the extracellular polymers before and after UV / peracetic acid disinfection; Step S42 further includes the following steps: Step S421. The molecular formulas before and after UV / peracetic acid disinfection are matched, and the known CHO compounds in the soluble organic matter are used for internal standard calibration. After calibration, the molecular formula matching is performed according to the following parameters: S / N>4, the number of elements is as follows, C 1-∝ , H 1-∝ , O 1-∝ , N 0-3 , S 0-1 , and obtain the possible molecular formula results; Step S422. Further screen the possible molecular formula results of step S421, and retain the molecular formulas with 0.2<=H / C<=2.3 and 0<=O / C<=1.2; Step S423. Retain the molecular formulas with DBE-O values ​​in the range of -10 to 10. If one m / z value corresponds to multiple possible molecular formulas, retain the molecular formula with the smallest number of heteroatoms. If there are still non-unique molecular formulas, retain the molecular formula with the smallest error value; the number of heteroatoms is the sum of N+S. Step S424. Analyze the mass spectrum peaks with m / z values ​​ranging from 100-800 Da.

2. The method according to claim 1, characterized in that: The concentration of peracetic acid in the water in step S1 is 10 mg / L, the stirring speed is 100 rpm, and the stirring time is 2 min.

3. The method according to claim 1, characterized in that The radiation dose of ultraviolet irradiation in step S2 is 108 mJ / cm 2 .

4. The method according to claim 1, characterized in that: In step S1, the extracellular polymers include soluble extracellular polymers, loosely bound extracellular polymers and tightly bound extracellular polymers. The extracellular polymers are extracted from the secondary effluent of the sewage treatment plant by ultrasonic-thermal extraction. The extraction method comprises the following steps: Step a. providing a uniformly mixed sludge mixture, centrifuging the sludge mixture, and then filtering the supernatant with a filter membrane, and taking the filtrate as the soluble extracellular polymer; Step b. Add 0.01 mol / L sodium chloride solution to the sludge after centrifugation in step a to the original volume of the sludge mixture, sonicate, centrifuge, and then filter the supernatant with a filter membrane to obtain the filtrate, which is the loosely bound extracellular polymer; Step c. Remove the supernatant from the remaining sludge in step b, add 0.01 mol / L sodium chloride solution to the original volume of the sludge mixture, and place in a 70-90°C water bath for 20 min-40 min, centrifuge, and then filter the supernatant through a filter membrane. The filtrate is the tightly bound extracellular polymer.

5. The method according to claim 4, characterized in that In step a, the centrifugation temperature is 1-4°C, the centrifugation speed is 8000 rpm-10000 rpm, and the centrifugation time is 8-10 min.

6. The method according to claim 4, characterized in that In step b and step c, the centrifugal speed is 10000 rpm-12000 rpm, the centrifugal time is 5 min-15 min, the ultrasonic time in step b is 4 min-10 min, and the ultrasonic frequency is 30 kHz-40 kHz.

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