A method for tracing rainwater pipe mixing based on mass spectrometry

Abstract

The present application belongs to the field of municipal drainage pipe network engineering, and relates to a rainwater pipeline mixed connection tracing method. Specifically, the present application relates to a rainwater pipeline mixed connection tracing method based on mass spectrometry and application thereof. The rainwater pipeline industrial wastewater mixed connection tracing method comprises the following steps: a sample collection step, a sample pretreatment step, a sample characteristic substance screening step and a mixed connection tracing step, wherein the mass spectrometry methods used include but are not limited to GC-MS, ICP-MS, HPLC-MS and the like. The present application can determine whether industrial wastewater is mixed and the type of mixed industrial wastewater by comparing the types and response values of characteristic substances of rainwater pipeline outlets and industrial wastewater, so as to determine the source of industrial wastewater.

Description

Technical Field

[0001] This invention belongs to the field of municipal drainage pipe network engineering and relates to a method for tracing the source of mixed connections in rainwater pipes. Specifically, this invention relates to a mass spectrometry-based method for tracing the source of mixed connections in rainwater pipes and its application. Background Technology

[0002] Black and foul-smelling water during rainy days is becoming a major pollution problem for urban rivers in hot and rainy cities, with pipe pollution being a significant contributing factor. The problem of mixed connections in stormwater pipes is particularly serious, especially in industrial areas where industrial wastewater is commonly mixed with stormwater pipes. This mixing leads to the uncontrolled discharge of industrial wastewater, posing a potentially major source of pollution to receiving water bodies, thus necessitating urgent stormwater pipe renovation. The key to promoting this renovation lies in diagnosing the sources of industrial wastewater, i.e., source tracing.

[0003] Source tracing is challenging in real-world environments because cross-contamination is influenced by numerous factors, including regional development, climate and meteorology, groundwater levels, river connectivity, and pipeline construction levels, resulting in uncertainty and randomness. These factors further complicate source tracing. Industrial wastewater is diverse and far more complex than domestic or restaurant wastewater, exhibiting fundamentally different physicochemical properties compared to other water types such as sewage and surface water. A significant bottleneck in source tracing, particularly in addressing the uncertainty and difficulty in diagnosing complex cross-contamination areas of stormwater and industrial wastewater, lies in insufficient understanding of the characteristics of pollutants in the cross-contamination wastewater, especially the lack of relevant research methods.

[0004] Currently, commonly used source tracing methods include manual inspection, closed-circuit television (CCTV) video inspection, and physicochemical parameter methods. All of these methods require prying open manhole covers, which is very labor-intensive. Manual inspection relies on visual inspection and the experience of inspectors, and can accurately diagnose very limited types of industrial wastewater. CCTV is expensive. Physicochemical parameter methods typically use water quality characteristic factors for source tracing; this method is costly because it uses standard chemical substances. The water quality characteristic factors of most industrial wastewater are unknown, and since these factors differ for each type of industrial wastewater, source tracing is costly and difficult to implement in practice. Ammonia nitrogen levels in industrial wastewater are usually normal, so ammonia nitrogen cannot be used to diagnose mixed industrial wastewater connections. When faced with mixed connection cases, people often try to combine these methods based on experience, resulting in many ineffective attempts and failing to diagnose most types of industrial wastewater, leading to low efficiency and preventing the implementation of mixed connection remediation projects. Therefore, overcoming the challenge of low-cost, high-efficiency source tracing of mixed industrial wastewater connections in rainwater pipes has become crucial for accurate source control and pollution interception. Summary of the Invention

[0005] The technical problem to be solved by this invention is to develop a low-cost, high-efficiency method that can easily and efficiently diagnose the source of industrial wastewater, has practical application value for tracing the source of mixed industrial wastewater in rainwater pipes in industrial areas, and is of great significance for the comprehensive management of urban water environment.

[0006] This invention provides a method for tracing the source of mixed industrial wastewater in rainwater pipes, comprising the following steps:

[0007] S1, Sample collection steps: Collect water samples from before industrial wastewater treatment, after industrial wastewater treatment, and from the outlet of rainwater pipes as analytical samples, and filter and / or pre-treat them after collection.

[0008] S2, Sample pretreatment steps: Digest the sample, perform liquid-liquid extraction and solid-phase extraction respectively, and filter the pretreatment products;

[0009] S3, Characteristic substance screening steps for samples: Characteristic substances include characteristic organic and characteristic inorganic substances; the organic substances in the pretreatment products of liquid-liquid extraction and / or solid-phase extraction are analyzed using full scan technology based on gas chromatography-mass spectrometry (GC-MS) to screen characteristic organic substances; the inorganic substances in the digestion pretreatment products are analyzed using full scan technology based on inductively coupled plasma mass spectrometry (ICP-MS) to screen characteristic inorganic substances.

[0010] S4, Mixed Source Tracing Step: By comparing the types and response values ​​of characteristic substances in rainwater pipe outlets and industrial wastewater, the type of industrial wastewater is determined.

[0011] The mass spectrometry methods used above include, but are not limited to, GC-MS, ICP-MS, HPLC-MS (liquid chromatography-mass spectrometry, also known as liquid chromatography-mass spectrometry), etc.

[0012] Preferably, in step S1, samples are collected on dry days with more than 3 sunny days in the preceding period;

[0013] Collect industrial wastewater samples from the source of industrial wastewater during the period of industrial wastewater production, including pre-treatment industrial wastewater, treated industrial wastewater, or water samples from rainwater pipe outlets. Collect samples 3-5 times a day, mix them in equal volumes, and use them as samples. The next step should be carried out within 7 days of collection.

[0014] Preferably, for samples used to analyze inorganic substances, pretreatment is performed after sample collection: nitric acid solution is added to adjust the acidity to pH < 2. For samples used to analyze organic substances, two independent pretreatment methods are used: liquid-liquid extraction and solid-phase extraction.

[0015] Preferably, the digestion includes the following steps:

[0016] S2.1.1, Add nitric acid solution and hydrochloric acid solution to the sample to make the pH of the mixture < 2. For example, the ratio of the sample, nitric acid solution, and hydrochloric acid solution can be (40-70):(1-5):1, by volume.

[0017] S2.1.2, Heat the mixture obtained in step S2.1.1, and the heating temperature shall not exceed 85°C;

[0018] S2.1.3, continue heating, keeping the solution from boiling, until the sample evaporates to about 10 ml;

[0019] S2.1.4, maintain slight and continuous reflux for at least 30 minutes;

[0020] S2.1.5, rinse with deionized water and then bring to volume.

[0021] Preferably, liquid-liquid extraction includes the following steps:

[0022] S2.2.1, Take the filtered water sample and add dichloromethane;

[0023] S2.2.2 After shaking extraction, the mixture was allowed to stand, and the organic phase extract was collected after separation. After multiple experiments, it was found that when shaking 3 times, more types of organic compounds were obtained in the chromatogram, which can further improve the accuracy and diagnostic efficiency of subsequent detection and analysis.

[0024] S2.2.3 Place glass wool at the bottom of the drying column, fill it with anhydrous sodium sulfate, pre-wash the anhydrous sodium sulfate drying column with dichloromethane, place a concentration tube below the drying column, add the extract into the drying column, and collect the filtrate into the concentration tube.

[0025] S2.2.4, Concentrate the dried extract in a water bath at a temperature not exceeding 40℃ to 0.5-1mL;

[0026] S2.2.5, Use dichloromethane to bring the concentrate to a final volume of 1 ml.

[0027] Preferably, the solid-phase extraction pretreatment step includes:

[0028] S2.3.1 Cleaning of the solid phase extraction column: [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] 18 Solid phase extraction columns are installed on a solid phase extraction device. Ethyl acetate is added to each extraction column to allow the ethyl acetate to wash and flow out naturally, and the solvent is discarded.

[0029] S2.3.2 Activation of solid phase extraction column: Add methanol to each extraction column. Before the extraction column dries out, add ultrapure water. When there is 1 ml of ultrapure water remaining above the adsorbent, close the outlet valve and prepare to add water sample for enrichment.

[0030] S2.3.3 Adsorption extraction of samples: Connect the sample to be analyzed (1L) to the extraction column through a polytetrafluoroethylene (PTFE) tubing, and place the other end of the tubing into the sample vial to be tested; turn on the vacuum pump and adjust the flow rate of the water sample to about 10ml / min; after all the sample has passed through the extraction column, continue vacuum suction for 10min to dry the column.

[0031] S2.3.4 Elution of the extraction column: Keep the connecting lines connected, open the top of the solid phase extraction device, place the glass centrifuge tube in the extraction tank to collect the eluent; add 5 ml of ethyl acetate, 5 ml of dichloromethane, and 3 ml of a mixture of dichloromethane and ethyl acetate in a volume ratio of 1:1, add the mixture to the extraction column, and collect the eluent.

[0032] S2.3.5 Dehydration of eluent: Place glass wool at the bottom of the drying column, fill it with anhydrous sodium sulfate for washing, and discard the solution; place a concentration tube below the drying column, add the extract to the drying column, and use a mixture of dichloromethane and ethyl acetate at a volume ratio of 1:1 to wash the column and collect the eluent into the concentration tube.

[0033] S2.3.6 Concentration of eluent: Concentrate to 0.5-1 ml by nitrogen stripping, and heat in a water bath at a temperature not exceeding 40℃;

[0034] S2.3.7 Volume Adjustment: Use dichloromethane to adjust the volume of the concentrate to no more than 1 ml.

[0035] Preferably, in step S3, components with response values ​​(i.e., CPS values) of the same inorganic component that differ by more than 100 times among different industrial wastewaters are screened, and the response values ​​of the component at the effluent outlet and in the industrial wastewater are compared.

[0036] When the response value of the outlet is second only to that of a certain type of industrial wastewater, it indicates that the outlet has been mixed with that type of industrial wastewater.

[0037] Export the NIST spectral library search report from GC-MS, screen components with a matching degree greater than 80% in the report as candidate characteristic organic compounds, compare the candidate characteristic organic compounds among different industrial wastewaters, and screen those that are unique to industrial wastewater as characteristic organic compounds.

[0038] Preferably, the filtration is performed by filtering the water sample using a filter membrane with a pore size of no more than 0.45 μm.

[0039] Preferably, the nitric acid solution is a solution obtained by mixing concentrated nitric acid and deionized water in equal volumes.

[0040] Preferably, the hydrochloric acid solution is a solution obtained by mixing concentrated hydrochloric acid and deionized water in equal volumes.

[0041] Preferably, in step S4, when the characteristic organic matter of a wastewater source is detected in the effluent analysis sample and the matching degree is greater than 80%, it indicates that the effluent is mixed with industrial wastewater corresponding to the wastewater source.

[0042] Preferably, when collecting water samples, the process also includes conducting a thorough survey of the sampling site, analyzing the types of industrial wastewater, and collecting information on the chemical raw materials used in industrial production and industrial wastewater treatment.

[0043] Preferably, the instrumental measurement steps for analyzing the sample include analyzing the inorganic and organic components of the sample.

[0044] Inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the inorganic components of the sample. The instrument parameters were set as follows: When developing the analytical method, select "semi-quantitative" in the "peak pattern" window under the "spectrum acquisition parameters" window; select all measurable elements in the periodic table as target elements.

[0045] The organic components of the samples were analyzed using gas chromatography-mass spectrometry (GC-MS). The instrument parameters were set as follows: mass spectrometry scan range 45-500 amu, ion source temperature 280°C, interface transfer temperature 280°C; scan time: 1 s / s, at least 5 scans per peak; column flow rate 1 ml / min; injection port temperature 250°C; splitless injection; injection volume 1 μL; a multi-stage temperature program was used: 50°C for 1 min, rapid ramp to 130°C, hold for 3 min, ramp to 180°C at 12°C / min, ramp to 240°C at 7°C / min, and ramp to 300°C at 12°C / min; data collection began at 4 min.

[0046] The present invention provides a method for tracing the source of mixed industrial wastewater in rainwater pipes, which can determine whether industrial wastewater has been mixed in based on water samples from the rainwater pipes; if industrial wastewater has been mixed in, the source of the industrial wastewater can be determined.

[0047] Preferably, by comparing the pollution characteristics of water samples from rainwater pipe outlets and industrial wastewater, the source can be traced, the solution for the mixed connection and renovation of rainwater pipes can be clarified, and a basis can be provided for exploring methods to remove pollutants from industrial wastewater in rainwater pipes.

[0048] The beneficial effects of this invention are as follows:

[0049] First, the commonly used water quality characteristic factor method is expensive due to the use of various standard products. This invention does not require the use of chemical standard products, which greatly reduces costs.

[0050] Secondly, existing technologies all require prying open the manhole covers of a large number of rainwater pipe inspection wells, while this invention does not require prying open the manhole covers, greatly reducing the amount of manpower and material resources required.

[0051] Third, existing technologies typically only obtain one or a few indicators per measurement, resulting in a very limited range of detectable industrial wastewater types and high costs. Some indicator detections may conflict. This invention overcomes these potential conflicts during the detection of different indicators, offering high throughput by simultaneously obtaining the relative contents of hundreds of organic compounds and dozens of inorganic compounds. By comparing differences between different samples, it can detect multiple types of industrial wastewater with high efficiency.

[0052] Fourth, compared with traditional technologies that only analyze a single water quality characteristic factor, a single chemical characteristic, or a single physical characteristic of a sample, this technology analyzes the organic and inorganic pollution characteristics of the sample in a comprehensive and systematic way. By comparing the pollution characteristics of the effluent and industrial wastewater, the source can be traced. The more comprehensive analysis of pollution characteristics improves the accuracy of source tracing. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, each drawing described below is for a part of the embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of a method for tracing the source of mixed connections in rainwater pipes proposed in this invention.

[0055] Figure 2 Data illustration for an embodiment of the present invention Figure 1 .

[0056] Figure 3 Data illustration for an embodiment of the present invention Figure 2 . Detailed Implementation

[0057] like Figure 1 As shown, this invention provides a method for tracing the source of mixed industrial wastewater in rainwater pipes, including steps such as data collection and research, sample collection and pretreatment, pretreatment and instrumental analysis, screening of characteristic substances, and tracing the source of mixed wastewater. Data collection and research includes pollution source investigation and collection of pipe network data. Sample collection and pretreatment includes filtering and pretreating industrial wastewater before treatment, industrial wastewater after treatment, and water samples at the rainwater pipe outlet.

[0058] To screen and analyze characteristic elements in industrial wastewater, the pretreatment process includes digestion, semi-quantitative mode of inductively coupled plasma mass spectrometry (ICP-MS), and detection of trace element response values. To determine characteristic organic compounds in the industrial wastewater, the pretreatment process includes liquid-liquid extraction and solid-phase extraction, using a full-scan mode to detect organic compound response values. After detecting and screening characteristic substances, source tracing is performed: specifically, the characteristic pollutant types and response values ​​of the effluent and the industrial wastewater are compared to determine the type of industrial wastewater at the effluent, thereby identifying the source of the industrial wastewater.

[0059] This invention eliminates the need to pry open manhole covers. It employs liquid-liquid extraction for pretreatment, and utilizes full-scan technology based on gas chromatography-mass spectrometry (GC-MS) for organic matter characterization and screening. Simultaneously, it uses digestion for pretreatment, and employs full-scan technology based on inductively coupled plasma mass spectrometry (ICP-MS) for inorganic matter characterization and screening. By comparing the types and response values ​​of characteristic organic and inorganic substances at the effluent outlet and in the industrial wastewater, the type of industrial wastewater can be diagnosed.

[0060] The technical solution will be clearly and completely described below through embodiments of this application. Obviously, the described embodiments are only some preferred embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0061] Example

[0062] To address the challenges of low efficiency and high cost in tracing mixed industrial wastewater discharges, this invention provides a method for tracing the discharge of mixed industrial wastewater discharges through rainwater pipes, comprising the following steps:

[0063] Sample collection steps: Conduct a thorough survey of the sampling site, analyze the type of industrial wastewater, and collect information on chemical raw materials used in industrial production and wastewater treatment. Collect samples on dry days with more than 3 sunny days prior to the sampling. Collect water samples before industrial wastewater treatment, after industrial wastewater treatment, and from rainwater pipe outlets as analytical samples. When collecting industrial wastewater samples, collect samples every 3 hours between 8:00 AM and 5:00 PM (during the factory's working hours), for a total of 4 collections. Mix equal volumes of the 4 wastewater samples from each factory to obtain the factory's sample. Similarly, collect outlet samples every 3 hours within the same time period, mixing equal volumes of water samples to obtain the outlet sample. Industrial wastewater before treatment is collected from the wastewater pool before entering the treatment facility; industrial wastewater after treatment is collected from the factory's main wastewater discharge outlet. Record the corresponding collection time and location. Further processing should be carried out within 7 days. For samples used to analyze inorganic substances, after sample collection, add an appropriate amount of nitric acid solution (concentrated nitric acid to deionized water volume ratio of 1:1) to adjust the acidity to pH < 2.

[0064] Filtration steps for sample analysis: To determine the organic components of the sample, the collected sample was pretreated by filtration using a 0.45 μm glass fiber membrane, and the volume of the water sample was recorded. Samples used to determine the inorganic components of the sample do not require filtration or other pretreatment.

[0065] Sample pretreatment steps: To determine the organic components of the sample, two independent pretreatment methods are used: liquid-liquid extraction and solid-phase extraction (SPE). Liquid-liquid extraction is simple to operate and can extract organic compounds with high content in the sample. The specific operation is as follows: 1. Measure 200 ml of filtered water sample using a graduated cylinder. Pour the filtrate into a separatory funnel (size: 500 ml) and add 20 ml of dichloromethane. 2. Shaking: Shake for 5 min, then let stand for 20 min. Collect the organic phase extract after separation. 3. Dehydration: Place a small amount of glass wool at the bottom of the drying column, fill it with anhydrous sodium sulfate to a height of 5-10 cm, and pre-wash the anhydrous sodium sulfate drying column twice with an appropriate amount of dichloromethane, discarding this part of the solution. Place a graduated KD concentration tube below the drying column, add the extract to the drying column, and collect the filtrate into the KD concentration tube. 4. Concentration: Concentrate the dried extract using a nitrogen blower, with the water bath temperature not exceeding 40℃, to 0.5-1 mL. 5. Volume adjustment. The concentrate was brought to a final volume of 1 ml using dichloromethane. A laboratory blank sample was prepared using water instead of the sample, following the same procedure.

[0066] Solid-phase extraction (SPE) pretreatment is slightly more complex than liquid-liquid extraction (LC-LI) and can extract trace organic compounds in low concentrations from analytical samples. The steps are as follows: 1. Cleaning the solid-phase extraction column. [The text then abruptly shifts to a different topic:] ...C 181. Solid-phase extraction (SPE) columns are installed on the SPE apparatus. Add 5 ml of ethyl acetate to each column, allowing it to flow out naturally without starting the vacuum pump. Repeat the cleaning process with 5 ml of dichloromethane, then discard all solvent. 2. Activation of the SPE columns: Add 10 ml of methanol to each column. Before the column dries out, add 10 ml of ultrapure water. When approximately 1 ml of ultrapure water remains above the adsorbent, close the outlet valve, preparing for water sample enrichment. 3. Sample adsorption and extraction: Connect the sample to be analyzed (1 L) to the extraction column via a PTFE tubing. Place the other end of the tubing into the sample vial. Turn on the vacuum pump and adjust the water flow rate to approximately 10 ml / min. After all the sample has passed through the extraction column, continue vacuum aspiration for 10 min to dry the column. 4. Elution of the extraction columns: Keep the tubing connected, open the top of the SPE apparatus, and place a glass centrifuge tube in the extraction chamber to collect the eluent. Add 5 ml of ethyl acetate, 5 ml of dichloromethane, and 3 ml of a 1:1 mixture of dichloromethane and ethyl acetate to the extraction column, and collect the eluent. 5. Dehydrate the eluent. Place a small amount of glass wool at the bottom of the drying column, then fill it with 5-10 cm of anhydrous sodium sulfate (5-7 g), and discard this portion of solution. Place a KD concentration tube below the drying column, add the extract to the drying column, and wash the drying column twice with a suitable amount of a 1:1 mixture of dichloromethane and ethyl acetate, collecting the eluent in the KD concentration tube. 6. Concentrate the eluent. Concentrate to 0.5-1 ml using nitrogen gas, heating in a water bath at a temperature not exceeding 40℃. 7. Make up to volume. Make up to 1 ml of the concentrate using dichloromethane. Prepare a laboratory blank sample using experimental water instead of the sample, following the steps above.

[0067] To determine the inorganic components of the sample, a pretreatment process, namely digestion, is performed. The steps are as follows: Accurately measure 50 mL of the well-mixed analytical sample into a 100 mL PTFE beaker. Add 2 mL of nitric acid solution (concentrated nitric acid to deionized water volume ratio 1:1) and 1 mL of hydrochloric acid solution (concentrated hydrochloric acid to deionized water volume ratio 1:1) to the beaker. Place the beaker on a hot plate for digestion, and the heating temperature should not exceed 85°C. During digestion, the beaker should be covered with a watch glass or other measures should be taken to ensure that the sample is not contaminated by the environment around the fume hood. Continue heating, keeping the solution from boiling, until approximately 10 mL of sample evaporates. Cover the beaker with a watch glass to reduce excessive evaporation and maintain gentle, continuous reflux for 30 minutes. After the sample cools, rinse the beaker with deionized water at least three times, and pour the rinsing solution into a volumetric flask. Ensure that the digestion solution is transferred to a 25 mL volumetric flask, dilute to volume with deionized water, cap, mix well, and store. If some insoluble matter is present in the digestion solution, it can be allowed to stand overnight or centrifuged to obtain a clear solution (if there is still suspended matter after centrifugation or standing overnight, it can be removed by filtration, but possible contamination during filtration should be avoided). Prepare a laboratory blank sample using experimental water instead of the sample, following the steps described above.

[0068] Instrumental analysis procedures for the samples: Inorganic components of the samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Instrument parameters were set as follows. When developing the analytical method, select "semi-quantitative" in the "peak pattern" window under "spectrum acquisition parameters". Select all measurable elements from the periodic table as target elements. Organic components of the samples were analyzed using gas chromatography-mass spectrometry (GC-MS). Instrument parameters were set as follows: Mass spectrum scan range: 45-500 amu. Ion source temperature: 280℃, interface transfer temperature: 280℃. Scan time: 1 s / s, at least 5 scans per peak. Column flow rate: 1 ml / min. Injector temperature: 250℃. Injection method: splitless injection. Injection volume: 1 μL. A multi-stage heating program was used: 50℃ held for 1 minute, rapidly increased to 130℃, held for 3 minutes, then increased to 180℃ at a rate of 12℃ / min, to 240℃ at a rate of 7℃ / min, and finally to 300℃ at a rate of 12℃ / min. Data collection began at 4 minutes.

[0069] The characteristic substance screening steps for the analysis samples are as follows: Components with response values ​​(CPS values) of the same inorganic component differing by more than 100 times among different industrial wastewaters are screened. The response values ​​of this component are compared between the effluent and the industrial wastewater. When the response value of the effluent is second only to that of a certain type of industrial wastewater, it indicates that the effluent has been mixed with that type of industrial wastewater. The NIST spectral library search report is exported from the GC-MS. Components with a matching degree greater than 80% in the report are selected as candidate characteristic organic compounds. These candidate characteristic organic compounds are compared among different industrial wastewaters, and those unique to each industrial wastewater are selected as characteristic organic compounds. When a characteristic organic compound is detected in the effluent sample with a matching degree greater than 80%, it indicates that the effluent has been mixed with the industrial wastewater corresponding to that characteristic organic compound.

[0070] Taking the mixed wastewater from stormwater pipes within the catchment area of ​​the Zhaoming stormwater pumping station in Ma'anshan City, Anhui Province as an example, a field survey was first conducted on the problematic pipe sections to determine the type of industrial wastewater and the industrial production situation. The survey revealed that industrial wastewater was being mixed into the stormwater pipes within the catchment area of ​​the Zhaoming stormwater pumping station in Ma'anshan City, Anhui Province. Therefore, on sunny days with more than three consecutive sunny days, industrial wastewater samples were collected from the catchment area, including pre-treatment and post-treatment wastewater from five factories: Jinxing Titanium Dioxide Co., Ltd., Saint-Gobain Pipeline Co., Ltd., Farsun Technology Co., Ltd., Cosmochemical Co., Ltd., and Libai Daily Chemical Co., Ltd. Domestic sewage was collected from the sewage pipes in the catchment area, restaurant wastewater was collected from under the stormwater grates near restaurants, and water samples were collected from the stormwater pipe outlets. The results are shown in Table 1.

[0071] Table 1 shows the sampling samples for the rainwater pipe cross-connection tracing method proposed in this invention. After sample collection, a portion of the water sample from each sample was added to a hydrochloric acid solution (concentrated hydrochloric acid to deionized water volume ratio of 1:1) to adjust the pH to <2. This portion of the water sample underwent inorganic characteristic analysis. That is, after digestion pretreatment, ICP-MS was used for determination, and the response values ​​of each element for each water sample were plotted in the same bar chart, as shown below. Figure 2 As shown in the figure, the response value of titanium in the industrial wastewater before treatment by Jinxing Titanium Dioxide Co., Ltd. is the highest, more than 1,000 times that of other types. The response value of the effluent sample is second only to that of the industrial wastewater, indicating that the effluent was mixed with industrial wastewater from Jinxing Titanium Dioxide Co., Ltd.

[0072] Table 1 Wastewater samples and their sources

[0073]

[0074] For water samples undergoing organic characterization analysis, 200 mL of each sample was taken, filtered, and then subjected to liquid-liquid extraction pretreatment. Simultaneously, 1000 mL of each sample was taken, filtered, and then subjected to solid-phase extraction pretreatment. After pretreatment, nitrogen blowing, and volume adjustment, the samples were analyzed by GC-MS. The chromatograms of the industrial wastewater and effluent samples from Saint-Gobain Pipeline Ltd. after pretreatment including liquid-liquid extraction are shown below. Figure 3 As shown in (a) and (b), the overlapping spectra of the two water samples are as follows. Figure 3 (c) shows the NIST spectral library search report exported from GC-MS. Components with a matching degree greater than 80% in the report were selected as candidate characteristic organic compounds. The candidate characteristic organic compounds were compared among different industrial wastewaters, and those unique to the industrial wastewater were selected as characteristic organic compounds, as shown in Table 2. The name, peak time, peak area, and CAS number of each characteristic organic compound were recorded. Among them, the characteristic organic compound for Saint-Gobain Pipeline Ltd. was 4-ethylbenzaldehyde. The detection of 4-ethylbenzaldehyde in the effluent outlet sample indicates that the effluent outlet was mixed with industrial wastewater from Saint-Gobain Pipeline Ltd. (…). Figure 3 (d)).

[0075] Table 2 is a data illustration of an embodiment of the rainwater pipe cross-connection tracing method proposed in this invention.

[0076] Table 2. Sources of wastewater and their specific organic markers

[0077]

[0078] This invention applies mass spectrometry technology to the diagnosis of mixed connections in rainwater pipes, solving problems that current methods (ammonia nitrogen, biological indicators, physicochemical parameters, etc.) cannot address, thus successfully diagnosing the type of industrial wastewater involved in the mixed connections of rainwater pipes.

[0079] The embodiments described above are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be conceived by those skilled in the art within the scope of the technology disclosed in this application without creative effort should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims in this application.

Claims

1. A method for tracing the source of mixed industrial wastewater in rainwater pipes, characterized in that, Includes the following steps: S1, Sample collection steps: Select dry days with more than 3 sunny days in the early stage to collect samples; collect industrial wastewater before treatment, industrial wastewater after treatment, and water samples from rainwater pipe outlets during the period of industrial wastewater production from the source of industrial wastewater. Collect 3-5 times a day, mix them in equal volumes as samples, filter them after collection, and proceed to the next step within 7 days of collection. S2, Sample pretreatment steps: The samples are independently digested, liquid-liquid extracted, and solid-phase extracted, and the pretreatment products are filtered. In the digestion, nitric acid solution and hydrochloric acid solution are added to the sample to make the pH of the mixture < 2. In the liquid-liquid extraction, dichloromethane is used as the extraction solvent, and the extraction is performed three times with shaking. In the solid-phase extraction, C... 18 Solid-phase extraction column uses ethyl acetate and dichloromethane as elution solvents; S3, Characteristic substance screening steps: Characteristic substances include characteristic organic and characteristic inorganic substances; using full-scan technology based on gas chromatography-mass spectrometry (GC-MS), the pretreatment products of liquid-liquid extraction and solid-phase extraction are analyzed for organic characteristics to screen characteristic organic substances; the screening of characteristic organic substances is as follows: exporting the NIST spectral library search report from GC-MS, screening components with a matching degree greater than 80% in the report as candidate characteristic organic substances, comparing candidate characteristic organic substances among different industrial wastewaters, and screening those unique to industrial wastewater as characteristic organic substances; using full-scan technology based on inductively coupled plasma mass spectrometry (ICP-MS), the digestion pretreatment products are analyzed for inorganic characteristics; the instrument parameters of the ICP-MS are set as follows: when compiling the analytical method, select "semi-quantitative" in the "peak pattern" window under the "spectrum acquisition parameters" window; select all measurable elements in the periodic table as target elements. S4, Tracing the source of cross-contamination: By comparing the types and response values ​​of characteristic substances in the rainwater pipe outlet and the industrial wastewater, the type of industrial wastewater is determined. When the characteristic organic matter of a certain industrial wastewater is detected in the sample analyzed from the rainwater pipe outlet, and the matching degree is greater than 80%, it indicates that the rainwater pipe outlet has been cross-contaminated with that industrial wastewater. Screen for components whose response values ​​of the same inorganic component differ by more than 100 times between different industrial wastewaters, and compare the response values ​​of that component in the rainwater pipe outlet and the industrial wastewater. When the response value of that component in the rainwater pipe outlet is second only to the response value of a certain industrial wastewater, it indicates that the rainwater pipe outlet has been cross-contaminated with that industrial wastewater.

2. The method for tracing the source of mixed industrial wastewater in rainwater pipes according to claim 1, characterized in that, The digestion process includes the following steps: S2.1.1, Measure the sample into a beaker, add nitric acid solution and hydrochloric acid solution to the sample, and make the pH of the mixture < 2; S2.1.2, Heat the mixture obtained in step S2.1.1, with the heating temperature not exceeding 85°C; S2.1.3, continue heating, keeping the solution from boiling, until the sample evaporates to 10 ml; S2.1.4, keep refluxed for at least 30 minutes; S2.1.5, Rinse the beaker with deionized water and then transfer it to a volumetric flask and make up to volume; Liquid-liquid extraction includes the following steps: S2.2.1, Take the filtered water sample and add dichloromethane; S2.2.2, After shaking extraction, let stand, collect the organic phase extract after separation, and shake extraction 3 times; S2.2.3 Place glass wool at the bottom of the drying column, fill it with anhydrous sodium sulfate, pre-wash the anhydrous sodium sulfate drying column with dichloromethane, place a concentration tube below the drying column, add the extract into the drying column, and collect the filtrate into the concentration tube. S2.2.4, Concentrate the dried extract in a water bath at a temperature not exceeding 40°C to 0.5-1 mL; S2.2.5, Use dichloromethane to bring the concentrate to a final volume of 1 ml; The pretreatment steps for solid-phase extraction include: S2.3.1 Cleaning of the solid phase extraction column: [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] 18 Solid phase extraction columns are installed on a solid phase extraction device. Ethyl acetate is added to each extraction column for washing, followed by dichloromethane for washing, and the solvent is discarded. S2.3.2 Activation of solid phase extraction column: Add methanol to each extraction column. Before the extraction column dries out, add ultrapure water. When there is 1 ml of ultrapure water remaining above the adsorbent, close the outlet valve and prepare to add water sample for enrichment. S2.3.3 Adsorption extraction of samples: Connect the sample to be analyzed to the extraction column through a polytetrafluoroethylene (PTFE) tubing, and place the other end of the tubing into the sample vial; turn on the vacuum pump and adjust the flow rate of the water sample to 10 ml / min; after all the samples have passed through the extraction column, continue vacuum suction for 10 min to dry the extraction column. S2.3.4 Elution of the extraction column: Keep the connecting tubing connected, open the top of the solid phase extraction device, place the glass centrifuge tube in the extraction tank and collect the eluent; add 5 ml of ethyl acetate, 5 ml of dichloromethane, and 3 ml of a 1:1 mixture of dichloromethane and ethyl acetate to the extraction column in sequence, and collect the eluent. S2.3.5 Dehydration of eluent: Place glass wool at the bottom of the drying column, fill it with anhydrous sodium sulfate for washing, and discard the solution; place a concentration tube below the drying column, add the eluent to the drying column, wash the drying column with a 1:1 volume ratio of dichloromethane and ethyl acetate, and collect the eluent into the concentration tube. S2.3.6 Concentration of eluent: Concentrate to 0.5-1 ml using nitrogen blowing, and heat in a water bath at a temperature not exceeding 40°C; S2.3.7 Volume Adjustment: Use dichloromethane to adjust the volume of the concentrate to no more than 1 ml.

3. The method for tracing the source of mixed industrial wastewater in rainwater pipes according to any one of claims 1-2, characterized in that, The organic components of the samples were analyzed using gas chromatography-mass spectrometry (GC-MS). The instrument parameters were set as follows: mass spectrometry scan range: 45-500 amu; ion source temperature: 280°C; interface transfer temperature: 280°C; scan time: 1 s / s, at least 5 scans per peak; column flow rate: 1 ml / min; injection port temperature: 250°C; injection method: splitless injection; injection volume: 1 μL; a multi-stage temperature program was used: hold at 50°C for 1 min, increase to 130°C, hold for 3 min, increase to 180°C at a rate of 12°C / min, increase to 240°C at a rate of 7°C / min, and increase to 300°C at a rate of 12°C / min. The process of collecting water samples also includes surveying the sampling sites, analyzing the types of industrial wastewater, and collecting information on the chemical raw materials used in industrial production and industrial wastewater treatment.

4. The application of the method for tracing the source of mixed industrial wastewater in rainwater pipes according to any one of claims 1-3, characterized in that, Determine whether industrial wastewater has been mixed in by taking water samples from the rainwater pipes; if so, determine the source of the industrial wastewater.

5. The application according to claim 4, characterized in that, By comparing the pollution characteristics of water samples from rainwater pipe outlets with those of industrial wastewater, the source of pollution can be traced, and methods for removing pollutants from industrial wastewater in rainwater pipes can be determined.

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