Analytical methods for the generation and mechanism determination of soluble microbial products and disinfection by-products

Abstract

The present invention belongs to the technical field of biological water treatment, and discloses the generation characteristics of soluble microbial products and the generation and mechanism determination and analysis methods of disinfection by-products in the process of chlorine disinfection. The present invention successfully produced three distinguishable SMP subcomponent water samples, namely UAP, GBAP and EBAP, under experimental conditions for the first time. The present invention used the precursor ion scanning method of ultra-high performance liquid chromatography triple quadrupole mass spectrometry for the first time to analyze the halogenated polar DBPs produced by chlorine disinfection SMP, and used HR-MS to identify and confirm some emerging DBPs, and speculated on some DBPs conversion pathways of SMP. Halogenated nitrophenols, halogenated furoic acids and halogenated pyrroles are highly toxic DBPs common to SMPs. The present invention is conducive to ensuring the safety of wastewater reuse, controlling the risk of DBPs in water supply systems, and improving the health of drinking water.

Description

Technical Field

[0001] The invention belongs to the technical field of biological water treatment, and in particular relates to a generation characteristic of a soluble microbial product and a method for determining and analyzing the generation and mechanism of disinfection by-products during chlorine disinfection. Background Art

[0002] During the disinfection of drinking water, the reaction between disinfectants (such as chlorine, chloramine, etc.) and dissolved organic matter (DOM) and halides in the raw water can inadvertently lead to the formation of disinfection byproducts (DBPs) that are harmful to human health. Epidemiological and toxicological studies have confirmed that long-term drinking of chlorinated water containing DBPs is associated with increased risks of adverse health conditions such as bladder cancer and congenital heart defects. In many areas of China, lakes, reservoirs or rivers are common sources of drinking water, but upstream biologically treated urban wastewater is also usually discharged into river tributaries, becoming an important source of drinking water downstream. For example, in the Pearl River Delta region, it usually takes 2-3 days for such wastewater to reach the downstream drinking water treatment plant. Therefore, organic pollutants in wastewater or recycled water can also change the DOM composition of drinking water source water, leading to the formation of more DBPs in the drinking water supply system. Biological treatment is a common process for wastewater and reclaimed water treatment, and soluble microbial products (SMPs) are the main components of organic matter in the effluent of biologically treated wastewater. They are organic compounds released into the solution by microorganisms through substrate metabolism and microbial cell decay. They have been proven to be an important class of DBPs precursors and an important regulatory target in sewage treatment systems. Since SMPs are composed of a mixture of unknown compounds, and the traditional drinking water treatment process (enhanced coagulation) and advanced treatment process ozone-biological activated carbon (O3-BAC) cannot effectively remove SMPs, they are widely present in drinking water. In addition, the long-term use of BAC will also leak microorganisms, leading to an increase in SMPs. Therefore, the potential risk of drinking water DBPs derived from SMPs cannot be ignored.

[0003] Due to the different times when wastewater reaches downstream drinking water treatment plants, SMPs will undergo natural biodegradation in receiving water bodies, and their composition varies greatly with the time of biodegradation, which means that SMPs directly discharged in wastewater cannot accurately represent their true state in drinking water treatment plants. In order to understand the impact of the biodegradation process on the composition of SMPs, researchers divided SMPs into two categories based on the bacterial derivation stage: one is the utilization-associated products (UAPs) directly produced during substrate utilization in the early stage of metabolism; the other is the biomass-associated products (BAPs) directly produced by endogenous respiration in the late stage of metabolism and indirectly formed in biomass decay processes such as extracellular polymeric substances (EPS) hydrolysis and cell lysis. Based on this theory, Ni et al. further divided BAPs into growth-associated BAPs (GBAPs) produced during the microbial growth stage and endogenous-associated BAPs (EBAPs) produced during the endogenous stage. At present, most studies focus on the formation of SMPs and DBPs under different conditions (such as pressure conditions, MBR online chemical cleaning, solar irradiation, etc.), but lack of concentrated research on the formation of DBPs in SMPs subcomponents (under different growth stages), and the formation characteristics of DBPs derived from GBAP and EBAP are still unclear. Control variables start from the definition point of view, and understand SMPs from the perspective of organic matter changes, which is of great significance for studying the generation characteristics of organic components in drinking water and organic matter in reclaimed water effluent, as well as understanding the differences in DBPs generation when SMPs are DBPs precursors.

[0004] Recently, researchers have discovered some new halogenated polar DBPs in chlorinated drinking water using ultra-high performance liquid chromatography / electrospray ionization-triple quadrupole mass spectrometry (UPLC / ESI-tqMS) technology, mainly aromatic DBPs, including halogenated phenols, halogenated hydroxybenzoic acids, halogenated hydroxybenzaldehydes, halogenated salicylates, halogenated nitrophenols, halogenated benzoquinones, halogenated pyrroles, etc. In addition, high-resolution mass spectrometry (HRMS) was used to reveal the molecular formulas of about 800 halogenated polar DBPs in chlorinated drinking water. These identified aromatic DBPs have also been shown to be intermediates in the formation of smaller aliphatic DBPs (such as trihalomethanes, haloacetic acids, and haloacetonitriles). Given that halogenated aromatic DBPs are generally considered to have stronger developmental toxicity and chronic cytotoxicity than the commonly known halogenated aliphatic DBPs, their occurrence in the environment requires additional attention. At present, although some studies have explored the occurrence of halogenated polar DBPs in wastewater or activated sludge water, the organic precursors in these systems are often too complex and contain other wastewater organic compounds (such as EPS, intracellular organisms, cell debris, etc.), and the specific formation characteristics of halogenated polar DBPs produced by SMPs and SMPs subcomponents after separate chlorination are still unclear. Understanding the generation of aromatic DBPs produced by SMPs chlorination will help to more comprehensively evaluate the risk characteristics of SMPs in the drinking water disinfection process, find the DBPs components that need to be controlled first, and provide a theoretical basis and technical support for drinking water safety.

[0005] Through the above analysis, the problems and defects of the prior art are as follows:

[0006] First, SMPs discharged directly into wastewater cannot accurately represent their true state in drinking water treatment plants. Due to differences in the time when wastewater reaches downstream drinking water treatment plants, SMPs undergo natural biodegradation in receiving water bodies, and a more comprehensive assessment of SMPs is needed from the perspective of biological stages. Secondly, there is a lack of research on SMPs and their subcomponents at different growth stages, especially for BAP subcomponents (i.e., GBAP and EBAP), which is still in the theoretical stage. It is not clear what the characteristics of organic matter at different growth stages under detailed conditions are and what the formation characteristics of DBPs are. Finally, it is not clear what the generation of halogenated polar DBPs produced by SMPs alone after chlorination is, because the organic systems in existing studies on halogenated polar DBPs cannot exclude other interfering organic matter other than SMPs. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a production method of SMPs at different growth stages and the disinfection by-products and mechanisms formed during chlorine disinfection.

[0008] The present invention is achieved in that SMPs at different growth stages are produced under laboratory conditions by controlling the carbon source and the biodegradation time, i.e., the conversion process of UAP-GBAP-EBAP. The SMPs are characterized by the conversion of microbial product-like substances to higher levels of humic acid and fulvic acid-like substances, especially humic acid-like substances within the range of an excitation wavelength exceeding 400nm and an emission wavelength exceeding 450nm. These characteristics can be used as a basis for judging the type of SMPs contained in actual drinking water inlet. In addition, aliphatic DBPs and halogenated polar DBPs are produced during the chlorination process, and halogenated nitrophenols, halogenated furic acid and halogenated pyrroles are highly toxic DBPs common to SMPs. This helps to judge the most risky type of SMPs, especially to evaluate the DBPs risk brought by SMPs based on the biodegradation time between the sewage treatment plant and the drinking water plant.

[0009] Furthermore, a bioreactor is constructed, and the solution is cultured by organisms and then filtered through a filter membrane to obtain an SMPs solution.

[0010] Furthermore, the SMPs include UAP, GBAP and EBAP; the three SMPs are distinguished by controlling the carbon source sodium acetate and the biodegradation time, and the three SMPs are quantified by total organic carbon (TOC) analysis and ion chromatography (IC) analysis.

[0011] Furthermore, the ultraviolet absorbance of the samples at 254 nm was analyzed using an ultraviolet-visible spectrophotometer (UV-Vis), and the ultraviolet specific absorbance (SUVA) value was calculated. SUVA was positively correlated with biodegradability, UAP was easily biodegraded, and had the highest SUVA value. GBAP, a soluble metabolite secreted by microorganisms during the endogenous respiration phase, had a lower SUVA value, and EBAP had the lowest SUVA value.

[0012] Furthermore, the fluorescence excitation-emission matrix (EEM) was used to analyze the organic characteristics of the three SMPs; the main components of UAP were microbial metabolites, proteins, peptides and amino acids, the main components of GBAP were fulvic acid and humic acid, and EBAP had higher fulvic acid and macromolecular humic acid contents, and lower relative contents of proteins, peptides and amino acids. That is, in the process of the main categories of SMPs being transformed from UAP to GBAP and finally to EBAP, the characteristics of SMPs were the transformation of microbial product-like substances to higher levels of humic acid and fulvic acid, especially humic acid substances within the range of excitation wavelengths exceeding 400nm and emission wavelengths exceeding 450nm.

[0013] Furthermore, the disinfection process is chlorination disinfection. The chlorine dosage gradient is set to chlorine: carbon = 0.5:1, 1:1, 3:1; the chlorine contact time gradient is set to 1, 3, 9, 24 hours.

[0014] Furthermore, gas chromatography-electron capture detector (GC-ECD) was used to analyze 11 aliphatic DBPs produced by chlorinated SMPs samples.

[0015] Furthermore, the total concentration of aliphatic DBPs derived from the three SMPs was in the order of EBAP>UAP>GBAP. The highest production rate of aliphatic DBPs in EBAP was due to its relatively high proportion of humic acid structure. GBAP showed greater chlorine resistance and the lowest content of DBPs due to the competitive consumption of chlorine by part of the extracellular polymeric substances (EPS) present in GBAP.

[0016] Furthermore, with the increase of chlorine addition amount and chlorine contact time, the content of aliphatic DBPs produced by the three SMPs showed an upward trend.

[0017] Furthermore, among the three SMP water samples, EBAP, which was in a state of endogenous consumption for a long time, had the highest production of carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs) under various chlorine disinfection conditions; UAP was most affected by chlorine dose; GBAP was the SMPs most affected by contact time.

[0018] Furthermore, the precursor ion scanning (PIS) method of ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UPLC / ESI-tqMS) was used to analyze the halogenated polar DBPs produced by chlorine disinfection of SMPs, and the transformation pathways of some DBPs in SMPs were speculated. Some emerging DBPs were identified and confirmed using high-resolution mass spectrometry (HR-MS).

[0019] The generation characteristics of soluble microbial products and the mechanism of the generation and mechanism determination and analysis methods of disinfection by-products during chlorine disinfection, namely the hydrolysis pathway of HANs to HAAs when the amount of chlorine is increased; the hydrolysis pathway of the intermediate aromatic DBPs 3,5-dibromo-4-hydroxybenzoic acid / benzaldehyde to dibromo-2-furoic acid and finally to small molecular aliphatic DBPs such as 2-bromobutenedioic acid and bromochloroacetic acid.

[0020] Furthermore, the total organic halogen (TOX) was used to analyze the total DBPs content, and the total organic chlorine (TOCl) and total organic bromine (TOBr) contents were analyzed.

[0021] Furthermore, with the increase of chlorine dosage and chlorine contact time, the TOX content of the three SMPs showed an upward trend. The TOBr / TOX of GBAP and EBAP decreased with the increase of chlorine dosage and chlorination contact time, while the opposite was true for UAP. This is because BAP contains more phenolic hydroxyl structures than UAP.

[0022] Furthermore, in comparison with the most representative natural organic matter (NOM) in nature, it was found that the main components of NOM were humic acid-like and fulvic acid-like, which were higher than their percentage range in SMPs, while SMPs contained a higher proportion of microbial products and protein-like substances. The specific yield of THM and HAAs in NOM was higher than that in SMPs, while the specific yield of HANs in SMPs was higher. In addition, the TOX yield of NOM was higher than that of SMP.

[0023] Another object of the present invention is to provide a system for analyzing the generation characteristics of soluble microbial products and the generation and mechanism of disinfection by-products during chlorine disinfection, comprising:

[0024] Water sample preparation module: used to prepare three different SMP subcomponent water samples based on SMP definition classification and microbial growth stage;

[0025] Spectral measurement module: used to analyze the spectral characteristics of three types of SMP subcomponent water samples and their organic component ratio distribution;

[0026] Analysis and processing module: Based on the results of the spectral measurement module, the generation mechanism of disinfection by-products is studied and their risks in drinking water sources are assessed;

[0027] Control and Alert Module: Used to issue DBP risk alerts and SMP generation recommendations based on the results of the analysis and processing module.

[0028] Another object of the present invention is to provide a system for analyzing the generation characteristics of soluble microbial products and the generation and mechanism of disinfection by-products during chlorine disinfection, comprising:

[0029] Bioreactor: used to receive the treated activated sludge and wash it with ultrapure water with the same inorganic ion concentration as the biological culture solution to ensure the suspended solid concentration in the water sample;

[0030] Nutrient addition module: used to add sodium acetate and other trace elements to the bioreactor to ensure the activity and health of microorganisms;

[0031] Spectral measurement module: used to measure the spectral characteristics of SMP subcomponent water samples and the distribution of their organic components;

[0032] Analysis and processing module: Based on the data from the spectrometry module, chlorination conditions are set in stages to study the DBPs generation mechanism and assess its potential risks in drinking water sources;

[0033] Mass spectrometry module: equipped with UPLC / ESI-tqMS and HR-MS, specifically for analyzing halogenated polar DBPs, ensuring accurate identification of emerging halogenated DBPs;

[0034] Control and output module: Provides rapid data analysis results of microbial products and DBPs, and gives corresponding treatment suggestions.

[0035] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0036] First, due to the difference in the time when wastewater reaches the downstream drinking water treatment plant, SMPs undergo natural biodegradation in the receiving water body, so the SMPs directly discharged in the wastewater cannot accurately represent their true state in the drinking water treatment plant. It is more in line with the actual situation to evaluate SMPs from the perspective of biological stage, but the current research on SMPs and their subcomponents at different growth stages is relatively scarce, especially the research on BAP subcomponents (i.e., GBAP and EBAP) is still in the theoretical stage, and it is necessary to distinguish UAP, GBAP and EBAP through real production under experimental conditions. Therefore, based on the SMP definition classification and microbial growth stage, the present invention produces three different SMP subcomponent water samples according to its production mechanism. It was found that in the process of the main category of SMPs being converted from UAP to GBAP and finally to EBAP, SMPs will be converted from microbial product substances to higher levels of humic acid and fulvic acid substances, especially humic acid substances within the range of excitation wavelength exceeding 400nm and emission wavelength exceeding 450nm. And in this process, the SUVA value continues to decrease, which is positively correlated with biodegradability.

[0037] The present invention is the first to compare and analyze the generation and conversion characteristics of three different SMP subcomponents as DBPs precursors under different disinfection conditions, and study their DBPs generation and conversion mechanisms. It was found that the total concentration of aliphatic DBPs derived from the three SMPs was arranged in the order of EBAP>UAP>GBAP, and with the increase of chlorine addition and chlorine contact time, the aliphatic DBPs content produced by the three SMPs showed an upward trend. EBAP, which has been in an endogenous consumption state for a long time, has the highest production of carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs) under various chlorine disinfection conditions; UAP is most affected by chlorine dosage; GBAP is the SMPs most affected by contact time.

[0038] Since the organic systems in the existing studies on halogenated polar DBPs cannot exclude other interfering organic matter other than SMPs, it is still unclear how halogenated polar DBPs are generated by SMPs alone after chlorination. The present invention uses the precursor ion scanning method (PIS) of ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UPLC / ESI-tqMS) for the first time to analyze the halogenated polar DBPs generated by chlorine disinfection of SMP, and uses high-resolution mass spectrometry (HR-MS) to identify and confirm some emerging DBPs, and speculates on the transformation pathway of some DBPs of SMP.

[0039] At the same time, the present invention compares with the most representative natural organic matter (NOM) in nature, and explores the risk characteristics and main risk points of DBPs generation compared with actual organic matter in nature, which has important practical significance for improving the health of drinking water quality and expanding the scale of recycled water utilization. It was found that the proportion of humic acid and fulvic acid in NOM is higher than that in SMPs, and SMPs contain a higher proportion of microbial products and protein substances. The specific yield of unit THM and HAAs in NOM is higher than that in SMPs, and the specific yield of HANs in SMPs is higher. In addition, the TOX yield of NOM is higher than that of SMP. Considering that HANs have a higher toxicity risk than THMs and HAAs, the DBP risk of SMPs is higher than that of NOM in a water environment with a high elemental nitrogen content. The present invention understands the characteristics of SMP itself and the DBPs generated after disinfection, especially the generation and transformation mechanism of emerging DBPs, which provides a theoretical basis for further studying the DBP risks generated by SMP.

[0040] Second, compared to the traditional invention that uses SMPs directly discharged into wastewater as precursors, the present invention evaluates SMPs from the perspective of biological stages, which is more in line with the actual situation of natural biodegradation in receiving water bodies. Based on the SMP definition classification and microbial growth stage theory, the invention successfully produced three distinguishable SMP subcomponent water samples in the laboratory for the first time, namely UAP, GBAP and EBAP, and discovered some organic characteristics under different biological transformation times. These characteristics are helpful in determining the occurrence state and category of SMPs in the influent or receiving water bodies of drinking water treatment plants. It was also found that biodegradability is positively correlated with SUVA values, which helps to optimize the removal strategy of SMPs. Considering that SMPs are considered to be important DBPs precursors, the present invention analyzes the generation and transformation characteristics and generation and transformation mechanisms of these three SMP subcomponents under different chlorination disinfection conditions. It was found that EBAP, which was in an endogenous consumption state for a long time, had the highest production of carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs) under various chlorine disinfection conditions; UAP was most affected by chlorine dosage; GBAP was the SMPs most affected by contact time. In addition, the present invention fills the gap in the field of SMPs as halogenated polar DBPs precursors. For the first time, the present invention used the precursor ion scanning method (PIS) of ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UPLC / ESI-tqMS) to analyze the halogenated polar DBPs produced by SMPs after chlorine disinfection, and used HR-MS to identify and confirm some emerging DBPs, and speculated on some DBPs conversion pathways of SMPs. In order to facilitate practitioners to more accurately evaluate the risk characteristics of DBPs derived from SMPs, the present invention compares them with the most representative natural organic matter (NOM) in nature and finds that the specific yield of HANs in SMPs is higher. Therefore, in a water environment with a high elemental nitrogen content, the DBP risk of SMPs is higher than that of NOM, and the toxicity risk derived from SMPs should be taken seriously.

[0041] The present invention creates a new biological culture scheme that can produce three distinguishable SMP subcomponent water samples in the laboratory, namely UAP, GBAP and EBAP. The types and characteristics of disinfection byproducts derived from them are analyzed, the partial generation and transformation mechanisms are studied, and the risks caused by them in drinking water source water are evaluated, which can serve as a theoretical basis for further controlling the DBPs risk generated by SMP. Specifically: Since EBAP has the highest DBP specific yield and the widest environmental distribution, it is necessary to give priority to the risk of EBAP producing DBP, especially drinking water treatment plants that are far away from upstream wastewater treatment plants in a state of longer biodegradation time. Compared with drinking water treatment plants in a state of shorter and longer biodegradation time, drinking water treatment plants in a medium biodegradation time need to pay extra attention to GBAP, and a higher chlorine dose needs to be used for GBAP to reduce the toxicity risk of intermediates. In addition, in water environments with high nitrogen content, priority should be given to the toxicity risk derived from SMPs. The present invention is conducive to ensuring the safety of drinking water source water, the safety of wastewater reuse and recycled water, and controlling the DBPs risk in the water supply system to improve the health level of drinking water.

[0042] Third, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0043] (1) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0044] First of all, the invention is based on the SMP definition classification and microbial growth stage theory, and successfully produced three distinguishable SMP subcomponent water samples in the laboratory for the first time, namely UAP, GBAP and EBAP. Previously, this type of substance has always remained in the theoretical model stage and cannot be effectively separated and produced under laboratory conditions. The present invention also compares the DBPs formation characteristics of UAP, GBAP and EBAP alone as DBPs precursors after chlorination disinfection, especially the formation characteristics of halogenated polar DBPs, filling the gap in the field of SMPs as halogenated polar DBPs precursors. At present, there is no report on the formation of halogenated polar DBPs produced by SMPs and SMPs subcomponents after chlorination alone, and the system for halogenated polar DBPs is often too complicated, and its organic precursor contains other wastewater organic compounds (such as EPS, intracellular organisms, cell fragments, etc.), which cannot confirm which halogenated polar DBPs are produced by SMPs itself, nor can it compare the formation profile of this type of DBPs under different biological growth stages. The present invention uses ultra-high performance liquid chromatography / electrospray ionization-triple quadrupole mass spectrometry (UPLC / ESI-tqMS) technology to analyze the halogenated polar DBPs produced by SMPs after chlorine disinfection, and uses HR-MS to identify and confirm some emerging DBPs, speculates on some DBPs transformation pathways of SMPs, and reveals a group of high-risk DBPs that have emerged. This invention helps to more comprehensively evaluate the risk characteristics of SMPs in the process of drinking water disinfection, find DBPs components that need to be controlled first, and provide a theoretical basis and technical support for drinking water safety.

[0045] (2) The technical solution of the present invention solves a technical problem that people have been eager to solve but have never been able to solve successfully:

[0046] In many areas of China, lakes, reservoirs or rivers are common sources of drinking water, but biologically treated urban wastewater upstream is often discharged into river tributaries, affecting the source of drinking water downstream. SMPs, as the main organic matter in sewage wastewater, are crucial to ensuring drinking water safety. However, the time when wastewater reaches the downstream drinking water treatment plant is different, resulting in natural biodegradation of SMPs in the receiving water body. For example, it usually takes 2-3 days for such wastewater to reach the downstream drinking water treatment plant in the Pearl River Delta. Therefore, SMPs directly discharged in wastewater cannot accurately represent their true state in the drinking water treatment plant. In order to be more in line with the actual situation, SMPs need to be evaluated from the perspective of the biological stage.

[0047] Researchers have devoted considerable efforts to understand the effects of biodegradation processes on the composition of SMPs. According to the bacterial derivation stage, SMPs can be divided into two categories: utilization-associated products (UAPs) produced directly during substrate utilization in the early stage of metabolism, and biomass-associated products (BAPs) produced directly through endogenous respiratory processes and indirectly formed during biomass decay processes in the later stages of metabolism [such as extracellular polymeric substances (EPS) hydrolysis and cell lysis]. Some researchers have also proposed a unified theory of SMP and EPS production, and they concluded that BAPs are only formed by EPS hydrolysis and all EPS are in the solid phase. Based on this theory, Ni et al. further divided BAPs into growth-associated BAPs (GBAPs) produced during the microbial growth stage and endogenous-associated BAPs (EBAPs) produced during the endogenous stage. However, there is a lack of research on SMPs and their subcomponents at different growth stages, especially for BAP subcomponents (i.e., GBAP and EBAP), which are still in the theoretical stage. It is necessary to distinguish UAP, GBAP, and EBAP through real production under experimental conditions.

[0048] The present invention successfully produced three distinguishable SMP subcomponent water samples, namely UAP, GBAP and EBAP, under experimental conditions by controlling the carbon source and biodegradation time, combined with total organic carbon analysis and ion chromatography analysis techniques for quantitative analysis, and used excitation-emission matrix analysis to analyze the organic characteristics at different biotransformation times, which are helpful to determine the occurrence state and category of SMPs in the influent or receiving water of drinking water treatment plants.

[0049] In addition, the risk of disinfection by-products derived from SMP is also an important issue that needs to be addressed. At present, most studies focus on the formation of SMPs and DBPs under different conditions (such as pressure conditions, MBR online chemical cleaning, solar irradiation, etc.), but lack a concentrated study on the generation of DBPs in SMPs subcomponents (under different growth stages), and the formation characteristics of DBPs derived from GBAP and EBAP are still unclear. At present, although some studies have explored the occurrence of halogenated polar DBPs in wastewater or activated sludge water, the organic precursors in these systems are often too complex and contain other wastewater organic compounds (such as EPS, intracellular organisms, cell debris, etc.), and the specific formation characteristics of halogenated polar DBPs produced by SMPs and SMPs subcomponents after separate chlorination are still unclear. The present invention uses ultra-high performance liquid chromatography / electrospray ionization-triple quadrupole mass spectrometry (UPLC / ESI-tqMS) technology to analyze the halogenated polar DBPs produced by SMPs after chlorine disinfection, and uses HR-MS to identify and confirm some emerging DBPs, speculates on some DBPs transformation pathways of SMPs, and reveals a group of high-risk DBPs that have emerged. This invention helps to more comprehensively evaluate the risk characteristics of SMPs in the process of drinking water disinfection, find DBPs components that need to be controlled first, and provide a theoretical basis and technical support for drinking water safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 Graphs showing changes in DOC of soluble microbial products in (a) a UAP reactor and (b) a BAP reactor provided by embodiments of the present invention;

[0052] Figure 2 It is the excitation-emission matrix fluorescence spectrum (DOC=1.0 mg / L) of SMP produced under different substrate matrix conditions provided in the embodiments of the present invention;

[0053] Figure 3 is the excitation-emission matrix fluorescence spectrum (0-10d) of the UAP reactor at different biological culture times provided by the embodiment of the present invention;

[0054] Figure 41 is a graph showing changes in common aliphatic DBPs formed by three SMPs under different chlorination conditions provided in an embodiment of the present invention, wherein (a), (c), and (e) respectively represent the volatile DBPs concentrations of UAP, GBAP, and EBAP when the chlorination contact time is 3 hours and the Cl2:C ratio is 0.5:1, 1:1, and 3:1; (b), (e), and (f) respectively represent the volatile DBPs concentrations of UAP, GBAP, and EBAP when the Cl2:C ratio is 1:1 and the chlorination contact time is 1, 3, 9, and 24 hours;

[0055] Figure 5 The following are (a) MRM chromatograms (223→79, 225→79 / 81, 227→81) of UPLC-ESI-MS / MS in a chlorinated UAP water sample after biological cultivation for 3.5 days provided by an embodiment of the present invention, and (bd) product ion scans corresponding to mass-to-charge ratios of 223, 225, and 227, respectively; (e) HRMS mass spectra of ion clusters in the sample with mass-to-charge ratios of 223, 225, and 227;

[0056] Figure 6 UPLC / ESI-tqMSPIS variation spectra of three SMPs at m / z 79 under different chlorination conditions provided in an embodiment of the present invention, (ac) chlorinated UAP samples, chlorine dosage Cl2:C is 0.5:1, 1:1, 3:1 respectively; (df) chlorinated substrate-free BAP samples, chlorine dosage Cl2:C is 0.5:1, 1:1, 3:1 respectively; (df) chlorinated matrix-free BAP samples, chlorine dosage Cl2:C is 0.5:1, 1:1, 3:1 respectively; (eh) chlorinated samples with substrate BAP added, chlorine dosage Cl2:C is 0.5:1, 1:1, 3:1 respectively;

[0057] Figure 7 3 is a graph showing changes in TOX content in three SMP and NOM samples after chlorination provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0059] In view of the problems existing in the prior art, the present invention provides a generation characteristic of a soluble microbial product and a determination and analysis method and mechanism for the generation and mechanism of disinfection by-products during chlorine disinfection.

[0060] Generation of UAP and BAP

[0061] The present invention adopts two 20L simple bioreactors to culture SMP water samples, which are respectively set as UAP reactors and BAP reactors, and the collected activated sludge is washed with ultrapure water to remove the residual organic matter in the sludge, and the sludge is transferred to the bioreactor so that the suspended solid concentration in the water sample is about 100 mg / L. Sodium acetate is added as the only carbon source in the UAP reactor, and the concentration is 200 mg / L in terms of carbon. No external carbon source is added in the BAP reactor, so that the microorganism enters the endogenous respiration period and produces BAP, and then a nutrient solution containing trace elements such as calcium and magnesium ions and a phosphate buffer solution are added to the water sample to keep the pH of the water sample at about 7.2, and the water sample is placed in a biochemical incubator for light-proof culture, and the temperature is set to 20°C. An external air pump is used to aerate the water sample to ensure that there is enough oxygen in the water sample. The mixed water sample in the reactor is sampled and analyzed every 12 hours, and the water sample is passed through a 0.45μm cellulose acetate filter membrane. The filtered water sample is considered to be water containing UAP or BAP.

[0062] The present invention adopts sodium acetate as the sole carbon source for microorganisms, and uses ion chromatography (IC) to quantitatively analyze the residual concentration of acetate ions in the sample, thereby calculating the concentration value of sodium acetate. In the UAP reactor, the concentration of UAP (in terms of DOC) = total DOC - 0.4 * sodium acetate DOC. When the substrate is exhausted, the UAP in the water continues to degrade into BAP as a substitute substrate, so the concentration of BAP with increased substrate DOC = the total DOC concentration of the remaining water sample. In the BAP reactor, since no substrate matrix is ​​added all the time, the concentration of BAP without substrate (in terms of DOC) = the total DOC concentration.

[0063] The embodiment of the present invention uses the precursor ion scanning (PIS) method of ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UPLC / ESI-tqMS) to analyze the halogenated polar DBPs produced by chlorine disinfection of SMP, and uses HR-MS to identify and confirm some emerging DBPs, and speculates the transformation pathway of some DBPs of SMP.

[0064] Chlorine disinfection experiment

[0065] The chlorination disinfection experiment of SMPs was carried out in a 2L glass bottle. Before disinfection, 90mg / L sodium bicarbonate was added to replace calcium carbonate to simulate medium alkalinity, and 2mg / L sodium bromide with a bromide ion concentration was added as a bromine source. The disinfectant used a sodium hypochlorite solution with an effective chlorine content of 8.5%. The bottle was wrapped with tin foil to avoid light and placed in a biological incubator at 20 degrees Celsius for disinfection. After disinfection, the residual chlorine concentration in the water sample was determined by DPD titration, and 0.1mol / L sodium thiosulfate solution was added to quench the residual chlorine in the water.

[0066] Disinfection by-products determination method

[0067] Determination and pretreatment of volatile halogenated disinfection by-products

[0068] The determination of volatile DBPs mainly refers to the U.S. EPA 551.1 standard method to detect THMs, HANs and TCNM in water samples. The U.S. EPA552.3 standard method is used to extract HAAs in water samples. Before HAAs determination, they are derivatized with a methanol solution acidified with 10% sulfuric acid, and finally detected by GC-ECD.

[0069] The polar halogenated disinfection byproducts in the sample were separated using an HSS T3 column (2.1×100mm, column temperature of 35℃) with an injection volume of 5μL. The mobile phases used were methanol and water with a mobile phase flow rate of 0.40mL / min. The volume ratio of methanol / water was linearly changed from 5:95 to 90:10 in the first 8min, and then the ratio of methanol and water was changed to the initial ratio from 90:10 to 5:95 within 0.10min and maintained for 2.9min to balance the system. The parameters of the mass spectrometer were set as follows: ESI negative ion mode, capillary voltage 2.9kV, cone voltage 15V, cone gas flow 50L / h, ion source temperature 120℃, desolvation gas temperature 400℃, desolvation gas flow 800L / h, collision energy 15-40eV, collision gas was argon with a flow rate of 0.25mL / min, mass resolution 13.5, and the detection residence time of MRM mode was 0.05s.

[0070] Determination and pretreatment of halogenated polar disinfection by-products

[0071] The liquid-liquid extraction (LLE) method was used for the pretreatment of halogenated polar DBPs. The study found that halogenated polar DBPs contain carboxyl and / or phenolic anions, and low pH values ​​are conducive to maintaining these DBPs in a neutral form. Therefore, 1:1 sulfuric acid was used to acidify the water sample to pH ≤ 0.5 and Na2SO4 was added as a salting-out agent at a mass ratio of 10:1 to the water sample. Then methyl tert-butyl ether (MTBE) was added as an organic solvent. After separation and shaking in a separatory funnel, the separated liquids were placed in a 4°C refrigerator for more than 2 hours. When concentrated to 0.5 ml using a rotary evaporator, acetonitrile was added to replace the solvent and the sample was placed in a 4°C refrigerator away from light.

[0072] The extracted water samples were monitored and analyzed by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS / MS), and the total ionic strength (TII) was determined based on the measured precursor ion scanning mass spectrum. The relevant parameters of the precursor ion scanning detection operation were set as follows: the injection volume was 6 μL; the chromatographic column used was Acquity UPLC HSS T3 column (2.1×100 mm, 1.8 mm, Waters); the gradient eluent consisted of methanol and water: the ratio of methanol / water (V / V) changed linearly from 5 / 95 to 90 / 10 in the first 8 min, then returned to 5 / 95 in 0.1 min, and then the chromatographic column was re-equilibrated for 2.9 min; the flow rate was set to 0.4 mL / min; the column temperature was 35 °C; and the MS / MS was in negative ion mode. The MS parameters were optimized and set as follows: desolvation air temperature: 300°C; cone gas flow rate: 50 L / h; desolvation gas flow rate: 650 L / h; source temperature: 110°C; capillary voltage: 2.9 kV; cone voltage: 15 V. For the multiple reaction monitoring mode (MRM) and product ion scan mode (Product Ion Scan Mode), the collision energy was set to 26 EV.

[0073] Total organic halogen (TOX) analysis

[0074] AOX (Absorbable Organic Halogen) is absorbable halides. It refers to organic halides containing Cl, Br and I except F. AOX is part of total organic halogens TOX (Total Organic Halogen). Organic halogens generally do not exist in natural water bodies, and large amounts of AOX can only be detected in polluted water bodies. AOX can measure the generation of DBPs in water samples after disinfection.

[0075] The experiment measured the AOX of water samples with different biodegradation days after disinfection. Before the measurement, the water samples were acidified with 1 mol / L concentrated nitric acid to ensure that the pH was below 2. The AOX obtained can approximate the TOX (Total Organic Halogen) of the water sample when the pH was <2. During the measurement, the water sample entered the adsorption system, where TOX was adsorbed by the activated carbon column, and then the column was washed with pure water to remove the captured inorganic halides. The activated carbon column was then burned to convert the adsorbed TOX into HX gas. After collection, it was potentiometrically titrated with a microcoulomb detector. The HX gas content obtained during the titration was the total amount of AOX or TOX. The concentration of total organic chlorine (TOCl) and total organic bromine (TOBr) was determined by using ultrapure water to adsorb and collect the HX produced by the burning activated carbon column. After obtaining the TOX water sample, the concentrations of chloride ions and bromide ions were determined by ion chromatography, respectively, and then the TOCl and TOBr in the water were converted.

[0076] Based on the definition of SMPs at different bacterial derivation stages and the experience of other researchers in the laboratory culture and production of UAP and BAP, and combined with the theoretical model proposed by Ni et al., the present invention successfully produced three distinguishable SMP subcomponent water samples, namely UAP, GBAP and EBAP, under experimental conditions by optimizing the biological culture scheme. Its organic matter analysis results (including total organic carbon analysis, ion chromatography analysis and excitation-emission matrix analysis) are consistent with some results in other studies. For example, the distribution characteristics of soluble microorganisms, humic acid and fulvic acid of UAP and EBAP are consistent with the research results of Ma et al.; the humic acid substances detected in the present invention, especially those with an excitation wavelength of more than 400nm and an emission wavelength of more than 450nm, are also detected in real water bodies of drinking water sources seriously affected by sewage. Similarly, some highly toxic DBPs, such as halogenated pyrroles, are also detected in sewage effluent. These cases show that the invention is technically feasible, and compared with other studies, it is more helpful to more comprehensively evaluate the risk characteristics of SMPs in the process of drinking water disinfection, and provide a theoretical basis and technical support for drinking water safety.

[0077] Compared with the traditional invention that takes SMPs directly discharged into wastewater as precursors, the present invention evaluates SMPs from the perspective of biological stages, which is more in line with the actual situation of natural biodegradation in receiving water bodies. Based on the SMP definition classification and microbial growth stage theory, the invention successfully produced three distinguishable SMP subcomponent water samples in the laboratory for the first time, namely UAP, GBAP and EBAP, and discovered some organic characteristics under different biological transformation times. These characteristics are helpful to determine the occurrence state and category of SMPs in the influent or receiving water bodies of drinking water treatment plants. It was also found that there is a positive correlation between biodegradability and SUVA values, which helps to optimize the removal strategy of SMPs. Considering that SMPs are considered to be important DBPs precursors, the present invention analyzes the generation and transformation characteristics and generation and transformation mechanisms of these three SMP subcomponents under different chlorination disinfection conditions. It was found that EBAP, which was in an endogenous consumption state for a long time, had the highest production of carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs) under various chlorine disinfection conditions; UAP was most affected by chlorine dosage; GBAP was the SMPs most affected by contact time. In addition, the present invention fills the gap in the field of SMPs as halogenated polar DBPs precursors. For the first time, the present invention used the precursor ion scanning method (PIS) of ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UPLC / ESI-tqMS) to analyze the halogenated polar DBPs produced by SMPs after chlorine disinfection, and used HR-MS to identify and confirm some emerging DBPs, and speculated on some DBPs conversion pathways of SMPs. In order to facilitate practitioners to more accurately evaluate the risk characteristics of DBPs derived from SMPs, the present invention compares them with the most representative natural organic matter (NOM) in nature and finds that the specific yield of HANs in SMPs is higher. Therefore, in a water environment with a high elemental nitrogen content, the DBP risk of SMPs is higher than that of NOM, and the toxicity risk derived from SMPs should be taken seriously.

[0078] In summary, the present invention has created a new biological culture scheme that can produce three distinguishable SMP subcomponent water samples in the laboratory, namely UAP, GBAP and EBAP. The types and characteristics of disinfection by-products derived from them were analyzed, some of the generation and transformation mechanisms were studied, and the risks caused by them in drinking water source water were evaluated, which can serve as a theoretical basis for further controlling the risks of DBPs generated by SMP. Specifically: Since EBAP has the highest DBP specific yield and the widest environmental distribution, it is necessary to give priority to the risk of EBAP producing DBP, especially in drinking water treatment plants far away from upstream wastewater treatment plants. For drinking water treatment plants at medium distances, additional attention should be paid to GBAP, and higher chlorine doses should be used for GBAP to reduce the toxicity risk of intermediates. In addition, in water environments with high elemental nitrogen content, priority should be given to the toxicity risks derived from SMPs.

[0079] Analysis of the composition characteristics of UAP and BAP provided by the present invention.

[0080] 1) DOC changes under different biological culture time

[0081] Figure 1 The SMP variation diagram in the UAP reactor and the BAP reactor shows that the UAP reactor produced a large amount of UAP from 0 to 2 days, reaching a peak at 2 days, and then decreased with the further increase of biodegradation time. Figure 1 It can be found that the substrate sodium acetate has not been completely degraded at this time, but UAP has been gradually degraded with the increase of biodegradation time. A similar phenomenon was also found in the study of Ni et al. UAP only accumulated in the first half of biodegradation and degraded to a lower concentration with the substrate in the second half. Ni et al. found that UAP is mainly small molecules, but different researchers found that the proportion of small molecular weight in UAP varies greatly when studying the changes in UAP molecular weight. This is because the small molecule UAP produced in microorganisms is easily biodegraded into larger molecular UAP, and this reaction will proceed even if the substrate has not been completely consumed. Therefore, small molecule UAP is mainly produced from 0-2d, and larger molecular weight UAP is the main organic matter from 2-3.5d. The BAP reactor has been in an endogenous state, and generally increases with the increase of biological culture time, but it is not stable, accompanied by the degradation of BAP, indicating that increasing the biological reaction time can remove SMP, and BAP is not non-biodegradable, but the biodegradation rate is slow, so the decrease in DOC is caused by the degradation of some products in BAP.

[0082] 2) Comparison of water quality parameters such as pH, ammonia nitrogen, MLVSS and TDS of the reactor before extraction of SMPs of three SMPs

[0083] Table 1 Comparison of water quality parameters of three SMPs

[0084]

[0085] Table 1 compares the water quality parameters of the three SMP water samples. It can be seen that the three SMPs are all under biological culture conditions with a pH of about 7, indicating that there is no large-scale biological abnormality in the water. This is because the phosphate buffer solution was added before the biological culture to adjust the pH value of the system to ensure that the organisms are in a steady-state growth state. At the same time, it was found that there was no ammonia nitrogen in the three water samples. The ammonia nitrogen added in the nutrient solution has been completely degraded, so the nitrogen source has been fully utilized by microorganisms. The SUVA value reflects the degree of aromatic structuralization of organic matter in the water body. The higher the SUVA, the higher the content of aromatic organic matter in the water body. It can be seen that among the three SMPs, UAP has the highest SUVA value, followed by BAP with added substrate, and BAP without added substrate has the lowest SUVA value. UAP has a higher SUVA value, so UAP contains more aromaticity.

[0086] The present invention provides three-dimensional fluorescence spectrum (EEM) change analysis of UAP and BAP.

[0087] 1) Changes in three-dimensional fluorescence spectra under different substrate matrices

[0088] The SMP produced under different substrate conditions was compared and analyzed by EEM. Figure 2 ), it was found that SMP under different matrices all had fluorescence peaks in the following three regions, namely, region A: excitation wavelength 230 to 300nm, emission wavelength 250 to 390nm, this region represents microbial metabolites, proteins, peptides and amino acids; region B: excitation wavelength 230 to 300nm, emission wavelength 390 to 550nm, this region represents fulvic acid; region C: excitation wavelength 300 to 480nm, emission wavelength 340 to 550nm, this region represents humic acid.

[0089] However, there are also significant differences between the contents of different components in different samples. As can be seen from the figure, the fluorescent substances of UAP produced by biological culture for 3.5 days are mainly distributed in areas A and C, among which area A is the most prominent and higher than area C, which represents the dominant position of microbial metabolites, proteins, peptides and amino acids in UAP. After the UAP water sample was further cultured to the 10th day, it was found that the relative contents of areas B and C increased with the increase of biodegradation time, while the relative content of area A decreased. That is, with the increase of biological culture time, the accumulation of fulvic acid and humic acid substances in UAP increased, while microbial metabolites, proteins, peptides and amino acids decreased. The study found that the relative content of protein in UAP is greater than that of BAP. Since there is no substrate after 10 days of biological culture, UAP is further decomposed and utilized by microorganisms, while GBAP accumulates in the system. Therefore, GBAP is dominant in the system, which is consistent with the above fluorescence results.

[0090] For EBAP, which was not added with substrate matrix from beginning to end, it had more fulvic acid and humic acid substances and fewer microbial metabolites, and the fluorescence intensity of the fulvic acid area was greater than that of the microbial product area. Some researchers further subdivided BAP into growth-related BAP, namely GBAP, and endogenous-related BAP, namely EBAP. GBAP is produced during the growth period of microorganisms, with a MW of about 1000kDa, and EBAP is produced in the endogenous stage, with a molecular weight of 4500kDa, which is greater than GBAP. Therefore, although UAP and BAP water samples after 10 days of biological culture are essentially BAP, the UAP water sample first undergoes the growth stage to produce GBAP, and then produces EBAP in the endogenous stage. It is a mixture of GBAP and EBAP. Compared with the BAP water sample, which is mainly in the endogenous stage at the beginning, it has a higher GBAP content and a lower EBAP content. Therefore, the fluorescence difference between BAP water samples and UAP water samples after 10 days of biological cultivation is caused by the intrinsic differences between GBAP and EBAP. Interestingly, the fluorescence peak representing the D zone of large molecular weight humic acid also confirms this argument. The D zone content is the highest in BAP, while UAP after 10 days of biological cultivation also has some D zone fluorescence. Only a small amount of D zone fluorescence appears in UAP after 3.5 days of biological cultivation.

[0091] A comprehensive comparison of the three-dimensional fluorescence characteristics of UAP and BAP revealed that their peak areas were consistent but their contents were different. The main components of UAP were microbial metabolites, proteins, peptides and amino acids, while the main components of BAP were fulvic acid and humic acid. The fluorescence intensity of the fulvic acid area in BAP without substrate matrix was greater than that of the microbial product area. For water samples with BAP as the main component, whether the substrate had been added was also an important factor. BAP without substrate had higher fulvic acid and macromolecular humic acid content, and lower relative content of protein, peptide and amino acid. The reason can be attributed to the fact that compared with GBAP samples with substrate added, EBAP samples without substrate added had almost no growth stage, and had higher EBAP accumulation and lower GBAP content.

[0092] 2) Comparative analysis of the three-dimensional fluorescence spectrum change characteristics under different biological culture time

[0093] Figure 3The three-dimensional fluorescence spectrum water samples in the UAP reactor under different biological cultivation time, the EEM samples were measured every 0.5 days, it can be seen that with the increase of biodegradation time, the water samples changed from almost no fluorescence at 0 days to gradually producing soluble microbial products and protein substances, and in the UAP water samples with substrate matrix, the soluble microbial product area was slightly higher than the humic acid area, and with the increase of biodegradation time, humic acid became the corresponding highest area, and when the microorganisms were in an endogenous state, an obvious fulvic acid area was observed, which was consistent with the research results of BAP, indicating that the microorganisms were in an endogenous state at 10 days of biodegradation, and the SMP in the water was BAP (GBAP).

[0094] The present invention provides an analysis of structural changes in emerging disinfection by-products.

[0095] Since the isotopic abundance ratio of bromine in nature is approximately 79 Br: 81 Br = 1:1, and the isotopic abundance ratio of chlorine is about 35 Cl: 37 Cl=3:1. Since the matrix of water samples is usually quite complex, it contains a large amount of organic matter and a large amount of inorganic ions are irregularly distributed. These non-halogen ions are distributed on almost every mass number. In the traditional full-scan spectrum, halogen ions are often hidden by non-halogen ions, which makes it impossible to fully and accurately analyze the halogenated DBPs in water samples. Zhang et al. developed a new method for detecting halogenated DBPs in chlorinated water samples using the precursor ion scan (PIS) mode in ESI-tqMS based on the generation characteristics of DBPs in chlorinated disinfected water samples. This method first ionizes the compounds in the test sample by ESI, so that the molecular ions first pass through the first mass analyzer Q1 once, and then each molecular ion collides with the inert argon molecules in the collision chamber Q2 to produce ion fragments, which are then detected and screened in the second mass analyzer Q3. The PIS mode can screen out parent ions containing only halogen fragments, which effectively distinguishes halogenated compounds from non-halogenated compounds, because non-halogenated compounds cannot produce halogen ion fragments through collision. Therefore, PIS will be less interfered by non-halogen ions, and the abundance ratio of halogen ions is also consistent with the distribution law in nature, such as m / z 35:37=3:1, m / z 79:81=1:1. Therefore, special attention should be paid to the paired ion clusters with similar proportions in PIS, such as m / z 223 / 225 / 227, 229 / 231 / 233, 267 / 269 / 271, 268 / 270 / 272, etc. Taking m / z 223 / 225 / 227 as an example, its ion cluster abundance ratio is 3:4:1, containing one chlorine atom and one bromine atom ( Figure 5 ).

[0096] After the ion cluster is screened by PIS mode, it needs to be further confirmed by MRM mode. MRM mode is a detection method that simultaneously screens parent ions and daughter ions in Q1 and Q3. Therefore, compared with PIS mode, MRM mode focuses more on the analysis of a single substance. It also has the advantages of higher sensitivity and stronger selectivity, and can be used for quantitative analysis of target compounds. For example, m / z223 / 225 / 227 is set to (223→79, 225→79 / 81, 227→81). It can be seen from the MRM mode diagram that the abundance ratio of ion clusters 223 / 225 / 227 is 3:4:1, which further verifies the spectral information of PIS. It can be inferred that this substance contains one chlorine atom and one bromine atom. The retention time of this substance is 0.85 minutes, which is very short relative to the total chromatographic time of 11 minutes. In the reversed-phase chromatography composed of water and methanol as the mobile phase and HSS-T3 column as the stationary phase, the shorter peak time represents its strong polarity. Zhai et al. divided the retention time of halogenated compounds into three ranges: 0-2.5 minutes for halogenated aliphatic acids, 2.5-6.0 minutes for halogenated benzoic acids, and 6.0-8.0 minutes for halogenated phenols, i.e., halogenated fatty acids < halogenated benzoic acids < halogenated phenols. At the same time, when polar halogenated compounds contain more than one polar functional group, their RT will become shorter and move to the adjacent range. In addition, the relationship between RT and pKa also confirms this view, that is, the longer the RT, the larger the pKa.

[0097] Since the exact structural information cannot be obtained in both PIS mode and MRM mode, product ion scanning can be performed on the substance to obtain its collision product ion fragments, and its structural information can be obtained through relatively high intensity fragment ion clusters. The product ion scanning parameters are set to (223 / 225 / 227). The results show that its ion fragments remove one hydrogen bromide and one CO2, one bromide ion and one CO, such as Figure 4 As shown, 143 collides with 223 and removes one H 79 Br, 99 represents the removal of one CO2 on the basis of 143, and 116 represents the removal of one CO2 on the basis of 223. 79 Br is then stripped of the remaining CO. The remaining structure contains 35 Cl and a CO2 group, the remaining molecular weight is 116-35-44=37, so we can tentatively infer that its remaining structure is C3H, and therefore its molecular formula is inferred to be C5H2O3BrCl.

[0098] Since some standard compounds in DBPs are not commercially available, HRMS can be used to further identify the ion clusters detected by PIS, and the m / z value of the target compound can be accurately determined, thereby obtaining its accurate molecular formula information. It is generally believed that the conventional measurement error of the mass-to-charge ratio of a substance is less than 10ppm, and the molecular formula can be considered correct if the accuracy error is 5ppm. This ion cluster was also detected in the HRMS sample, and the same molecular formula C5H2O3BrCl was obtained. The error between the measured mass number and the accurate mass number of the substance was calculated to be 1.04ppm, which is less than the upper limit of 10ppm. Therefore, the corresponding molecular formula of m / z223 / 225 / 227 can be considered to be C5H2O3BrCl. At the same time, no literature reports on this substance have been found, so this substance is an emerging DBP that has not yet been discovered. Combined with the daughter ion information, it is speculated that it contains an independent hydroxyl group, and its molecular formula is speculated to be chlorobromo-2-furoic acid.

[0099] Embodiment 1:

[0100] Bioreactor-based system for the generation of soluble microbial products and analysis of volatile disinfection by-products

[0101] 1. Use activated sludge with stable biological activity and wash it multiple times with ultrapure water to remove the organic matter in the sludge to the maximum extent.

[0102] 2. The washed sludge is transferred to a specially designed bioreactor and sodium acetate is added as a carbon source to ensure that its concentration is 200 mg / L. During this process, the national standard method GB11901-89 is used to ensure that the initial suspended solids concentration in each reactor is the same, about 100 mg / L, to ensure optimal microbial activity.

[0103] 3. In the UAP reactor, the acetate ion concentration was continuously monitored until the sodium acetate was completely degraded.

[0104] 4. The concentrations of UAP and BAP were quantitatively analyzed using online ion chromatography and total organic carbon analyzer, and multiple repeated experiments were performed to ensure the accuracy and consistency of the results.

[0105] 5. Continuously monitor the optical characteristics of organic matter in the reactor, using UV-Vis spectrophotometer and excitation emission matrix (EEM) analysis, and calculate the SUVA value to evaluate the aromaticity of the sample and the dynamic changes of organic matter.

[0106] 6. The obtained UAP, GBAP and EBAP samples were normalized to the same DOC concentration, and the distribution characteristics of each component were qualitatively detected and the distribution differences of organic matter were compared to ensure the comparability between different organic matter and the scientific nature of the method.

[0107] 7. Set the gradient chlorine dosage and chlorine contact time. The chlorine dosage adopts the chlorine-carbon ratio to ensure that the effective concentration of chlorine will not change due to the difference in the initial DOC concentration of the sample.

[0108] 8. The pretreated chlorinated water samples were sent to a gas chromatograph-electron capture device (GC-ECD) for analysis of volatile DBPs.

[0109] 9. According to the dynamic change law of organic matter and the generation trend of DBPs, the main risk characteristics of DBPs in SMPs at different biological stages are determined. Combined with the actual distribution of drinking water, feasible solutions are provided for optimizing the drinking water disinfection process.

[0110] Embodiment 2:

[0111] Combined analysis system of disinfection byproducts of microbial products and chlorinated natural organic matter based on high performance chromatography

[0112] 1. Set up two groups of bioreactors, add the same amount of inorganic ions, and add phosphate buffer solution to adjust the pH value to 7.2. One group adds sodium acetate as the substrate matrix, and the other group does not add any additional organic matter. Light-proof measures are taken to prevent photochemical reactions, and a biological incubator is used to ensure consistent environmental temperature.

[0113] 2. The collected activated sludge is washed with ultrapure water to remove most of the organic matter in the sludge itself, and then added to the reactor at the same concentration to ensure that most of the organic matter is produced by microorganisms using the substrate.

[0114] 3. Three SMP samples were obtained according to different biodegradation times, and NOM samples with the same DOC concentration were introduced as a control group. The four organic samples were normalized for further comparison.

[0115] 4. The same chlorination conditions were used for all samples, and the changes in organic matter before and after chlorination were compared using EEM analysis.

[0116] 5. The total DBPs content and volatile DBPs content of the chlorinated samples were analyzed using total organic halogen (TOX) and GC-ECD, respectively.

[0117] 6. Use advanced UPLC / ESI-tqMS to qualitatively analyze halogenated polar DBPs in water samples and combine with high-resolution mass spectrometry (HR-MS) to identify possible emerging polar DBPs.

[0118] 7. Based on the analysis results of UPLC / ESI-tqMS and existing studies, find the types of DBPs with higher toxicity, evaluate the risk of DBPs produced by SMPs in various drinking water sources, and make corresponding treatment recommendations based on the experimental results.

[0119] 8. Based on the generation characteristics of all types of DBPs and combined with the changes in organic matter before and after chlorination, we can find the connection and mechanism between precursors and DBPs to provide a theoretical basis for reducing the risk of DBPs.

[0120] Through the above two embodiments, the generation characteristics of soluble microbial products and the generation mechanism of disinfection by-products during chlorine disinfection can be effectively measured and analyzed, thereby providing powerful technical support for water quality monitoring and management.

[0121] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for determining the generation mechanism of disinfection by-products of soluble microbial products during chlorine disinfection, characterized in that: The steps include: Two 20L simple bioreactors were used to culture the SMP water samples, which were set as UAP reactors and BAP reactors respectively. The collected activated sludge was washed with ultrapure water to remove the residual organic matter in the sludge, and the sludge was transferred to the bioreactor to make the suspended solid concentration in the water sample 100mg / L. Sodium acetate was added as the only carbon source in the UAP reactor at a concentration of 200mg / L in terms of carbon, and no external carbon source was added in the BAP reactor; Subsequently, trace element nutrient solution containing calcium and magnesium ions and phosphate buffer solution were added to the two groups of water samples to keep the pH of the water samples at 7.

2. The water samples were placed in a biochemical incubator to avoid light and cultured. The temperature was set at 20°C and an external air pump was used to aerate the water samples to ensure that there was enough oxygen in the water samples. The residual concentration of acetate ions in the water samples was quantitatively analyzed using ion chromatography, and the concentration of sodium acetate was then calculated. In the UAP reactor, the concentration of UAP, in terms of DOC = total DOC - 0.4 * sodium acetate DOC. When the substrate is exhausted UAP in water continues to degrade into BAP as a substitute substrate, so the concentration of BAP with increased substrate, calculated in DOC = the total DOC concentration of the remaining water sample; and in the BAP reactor, since no substrate matrix is ​​added, the concentration of BAP without substrate, calculated in DOC = the total DOC concentration; in the UAP reactor, when sodium acetate is not completely degraded, the SMPs obtained are UAP, and after sodium acetate is completely degraded by microorganisms and enters the endogenous state, the SMPs obtained are GBAP, and EBAP is produced in the BAP reactor; Continuously monitor the optical characteristics of organic matter in the reactor, use UV-visible spectrophotometer and excitation emission matrix analysis, and calculate the SUVA value to evaluate the aromaticity of water samples and the dynamic changes of organic matter; set gradient chlorine dosage and chlorine contact time to disinfect each water sample; EEM was used to analyze and compare the changes in organic matter in each water sample before and after chlorine disinfection; the total DBPs content in the water sample after chlorine disinfection was determined by a total organic halogen analyzer, and the volatile DBPs content in the water sample after chlorine disinfection was analyzed by GC-ECD; the halogenated polar DBPs in the water sample were qualitatively analyzed by the precursor ion scanning method of UPLC / ESI-tqMS, and the emerging polar DBPs were identified by combining high-resolution mass spectrometry; Based on the generation characteristics of all types of DBPs and combined with the changes in organic matter before and after disinfection, the connection and mechanism between precursors and DBPs are sought.

2. The method according to claim 1, characterized in that The chlorine disinfection experiment of SMPs was carried out in a 2L glass bottle. Before disinfection, 90mg / L sodium bicarbonate was added, and sodium bromide with a bromide ion concentration of 2mg / L was added as a bromine source. The disinfectant used was a sodium hypochlorite solution with an effective chlorine content of 8.5%. The bottle was wrapped with tin foil to avoid light and placed in a biological incubator at 20 degrees Celsius for disinfection.

3. The method according to claim 1, characterized in that The invention relates to a method for determining the contents of total organic halogen, total organic chlorine and total organic bromine. The method comprises the following steps: before determination, firstly acidifying a water sample with 1 mol / L concentrated nitric acid to ensure that the pH value is below 2; during determination, placing the water sample into an activated carbon column for adsorption; then washing the column with pure water to remove captured inorganic halides; then burning the activated carbon column to convert the adsorbed total organic halogen into HX gas; and then performing potentiometric titration with a microcoulomb detector after collection. The HX gas content obtained during titration is the total amount of total organic halogen; and the concentrations of total organic chlorine and total organic bromine are determined by using ultrapure water to adsorb and collect HX generated by the burned activated carbon column. After obtaining a total organic halogen water sample, the concentrations of chloride ions and bromide ions are respectively determined by using ion chromatography, and then the concentrations of total organic chlorine and total organic bromine in water are converted.

4. A system for analyzing the generation characteristics of soluble microbial products and the generation and mechanism of disinfection by-products during chlorine disinfection, characterized in that: include: Water sample preparation module: three different SMP subcomponent water samples were prepared, including culturing SMP water samples in two 20L simple bioreactors, which were set as UAP reactors and BAP reactors respectively; the collected activated sludge was washed with ultrapure water to remove residual organic matter in the sludge; the sludge was transferred to the bioreactor to make the suspended solid concentration in the water sample 100 mg / L; sodium acetate was added as the only carbon source in the UAP reactor with a concentration of 200 mg / L in terms of carbon; no external carbon source was added in the BAP reactor; then trace element nutrient solution containing calcium and magnesium ions and phosphate buffer solution were added to the two groups of water samples to keep the pH of the water samples at 7.2; the water samples were placed in a biochemical incubator for light-proof cultivation, the temperature was set at 20°C, and an external air pump was used to aerate the water samples to ensure that the water samples There is enough oxygen in the water; the residual concentration of acetate ions in the water sample is quantitatively analyzed by ion chromatography, and then the concentration of sodium acetate is calculated; in the UAP reactor, the concentration of UAP, in terms of DOC = total DOC-0.4*sodium acetate DOC, when the substrate is exhausted, the UAP in the water continues to degrade into BAP as a substitute substrate, so the concentration of BAP with added substrate, in terms of DOC = the total DOC concentration of the remaining water sample; and in the BAP reactor, since there is no addition of substrate matrix, the concentration of BAP without substrate, in terms of DOC = the total DOC concentration; in the UAP reactor, when sodium acetate is not completely degraded, the SMPs obtained are UAP, and after sodium acetate is completely degraded by microorganisms and enters the endogenous state, the SMPs obtained are GBAP, and EBAP is produced in the BAP reactor; Spectrometry module: Use UV-visible spectrophotometer and excitation emission matrix analysis, and calculate the SUVA value to evaluate the aromaticity of water samples and the dynamic changes of organic matter; Analysis and processing module: including using EEM to analyze and compare the changes of organic matter in each water sample before and after chlorine disinfection; using a total organic halogen analyzer to determine the total DBPs content in the water sample after chlorine disinfection, and using GC-ECD to analyze the volatile DBPs content in the water sample after chlorine disinfection; using UPLC / ESI-tqMS precursor ion scanning method to conduct qualitative analysis of halogenated polar DBPs in water samples, and combining high-resolution mass spectrometry to identify the emerging polar DBPs; based on the generation characteristics of all types of DBPs, combined with the changes in organic matter before and after disinfection, to find the connection and mechanism between precursors and DBPs; Control and Alert Module: Used to issue DBP risk alerts and SMP generation recommendations based on the results of the analysis and processing module.

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