Method for rapidly detecting and identifying mixed connection and misconnection of urban pipe network based on VOCs tracer gas

Abstract

The invention discloses a method for rapidly detecting and identifying city pipe network mixed and misconnected based on VOCs tracer gas. The method comprises the following steps that S1, the distribution relation of rainwater pipes and sewage pipes in a target area is analyzed; s2, performing gas production analysis on the VOCs in the rainwater pipe and the sewage pipe to obtain spectrum data of the VOCs in the rainwater pipe and the sewage pipe, and selecting gas with unobvious background characteristics as tracer gas according to detection results of the spectrum data of the VOCs in the rainwater pipe and the sewage pipe; s3, selecting a tracer gas blowing point position, and blowing tracer gas into the pipeline; s4, according to the tracer gas blowing-in point position, VOCs in the inspection wells around the blowing-in point position and upstream and downstream are subjected to gas production, and TOF-MS is adopted for tracer gas detection; and S5, the detection condition of the tracer gas in each inspection well is analyzed, and the mixed and misconnected point positions of the rainwater pipe and the sewage pipe are rapidly determined. The method can quickly and accurately check the problem of mixed rain and sewage misconnection, and has the advantages of high economical efficiency, wide application range, high detection efficiency and low detection and identification cost.

Description

Technical Field

[0001] The present invention relates to the technical field of urban pipe network problem troubleshooting, and in particular to a method for identifying mixed and wrong connections in urban pipe networks based on rapid detection of VOCs tracer gas. Background Art

[0002] Tracer technology has long been a key tool in troubleshooting urban pipe network issues. However, current tracer techniques primarily rely on reagent tracing. This involves adding a brightly colored or fluorescent reagent to the pipe and observing the tracer downstream to determine if the pipe is connected. However, traditional tracing methods are significantly affected by pipe flow patterns, and tracer reagents often retain their color for a long time and are brightly colored, which can easily cause public panic about pollution incidents. Therefore, these methods are rarely used in practice.

[0003] In order to overcome the defects of the above-mentioned tracing technology, various new investigation technologies have been developed one after another. For example, patent application number CN201910007485.X discloses a system and method for rapid investigation of misconnections and missed connections in urban rainwater and sewage pipe networks. The present invention discloses a system and method for rapid investigation of misconnections and missed connections in urban rainwater and sewage pipe networks, the system comprising: a transmitting device, a plurality of receiving devices used in conjunction with the transmitting device, and a control module; the transmitting device is installed on a target manhole cover in a target area, and is used to transmit characteristic low-frequency sound waves into the manhole; each receiving device is respectively installed on other manhole covers except the target manhole cover in the target area, and is used to receive the characteristic low-frequency sound waves emitted by the transmitting device; the control module obtains each characteristic low-frequency sound wave received by each receiving device, and determines whether the pipe network in the manhole of the target area is misconnected or missed according to the low-frequency sound wave characteristic spectrum of each characteristic low-frequency sound wave.

[0004] This method uses sound waves as a tracer. By installing a low-frequency sound wave transmitter on a designated manhole cover and checking for low-frequency sound waves of various characteristics at other manhole covers, the method can analyze whether there are any mixed or misconnected pipes in the inspection area. However, it still has the following technical drawbacks: First, sound waves are easily interfered with. Underground pipelines are affected by many factors, such as water flow and above-ground road traffic, and their sound wave types, sizes, and other characteristics are easily disturbed. Second, the detection is relatively cumbersome and requires the installation of equipment at the inspection points in advance. Faced with a wide range and a large number of inspection wells, it is difficult to carry out the inspection work in a short time. Third, the accuracy of the results is difficult to guarantee. The transmission of sound waves in the pipeline is affected by factors such as pipes with different media, changes in pipe aperture, and damage points of different sizes. When faced with complex areas such as intersections, the analysis of the sound waves by the receiving device may contain errors. Therefore, this method still cannot provide practical help in large-scale inspections and has a limited scope of application. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to overcome the shortcomings of the existing technology and provide a method for quickly detecting and identifying mixed and wrong connections in urban pipelines based on VOCs tracer gas, thereby realizing rapid and accurate troubleshooting of pipeline problems and providing scientific guidance for subsequent pipeline engineering management.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a method for quickly detecting and identifying mixed and wrong connections in urban pipe networks based on VOCs tracer gas, comprising the following steps: S1. Sort out the basic situation of pipelines in the target area and analyze the distribution relationship between rainwater pipes and sewage pipes in the target area; S2. Conduct gas sampling and analysis of VOCs in rainwater pipes and sewage pipes, detect the VOCs composition in the rainwater pipes and sewage pipes, obtain the detection results of the VOCs spectrum in the rainwater pipes and sewage pipes, and select non-toxic, volatile gases with no obvious background characteristics as tracer gases; S3. Select a tracer gas injection point and inject the tracer gas into the pipeline; S4. Based on the tracer gas injection point, VOCs are sampled in representative inspection wells around the tracer gas injection point and upstream and downstream, and tracer gas detection is performed using TOF-MS high-resolution detection technology; S5. Analyze the detection of tracer gas around the tracer gas injection point and in the upstream and downstream inspection wells to quickly determine the connectivity between the pipelines and the mixed connection points of rainwater pipes and sewage pipes.

[0007] Furthermore, in step S1, the representative inspection well is a pipeline key node inspection well or a pipeline starting well.

[0008] Furthermore, the specific operating steps of step S2 are: after collecting VOCs gas from the rainwater pipe and the sewage pipe with a collection tube, the VOCs gas is detected and analyzed based on the PTR-TOF-MS high-resolution detection technology to form a TOF-MS spectrum of VOCs in the rainwater pipe and the sewage pipe, and the TOF-MS spectrum data of VOCs in the rainwater pipe and the sewage pipe are obtained. According to the spectrum data, a non-toxic, volatile gas with no obvious background characteristics is selected as a tracer gas.

[0009] Furthermore, the conditions for VOCs gas detection and analysis using PTR-TOF-MS are: mass scanning range 1-500 amu, instrument vacuum degree less than or equal to 10 -4 Pa, drift tube pressure 50-500Pa.

[0010] Preferably, the instrument vacuum degree is equal to 10 -4 Pa.

[0011] Furthermore, the fact that the background characteristics of the tracer gas in step S2 are not obvious means that in the VOCs spectrum in the rainwater pipe and the sewage pipe, the response value corresponding to the tracer gas is less than one thousandth of the maximum response value.

[0012] Furthermore, in step S3, the tracer gas injection point is selected to be the upstream inspection well of the pipeline.

[0013] Furthermore, the specific operation steps of step S4 are: according to the tracer gas injection point, use a collection tube to collect VOCs in the vicinity of the tracer gas injection point and in representative inspection wells upstream and downstream, and detect and analyze the VOCs gas based on the PTR-TOF-MS high-resolution detection technology to detect whether there is tracer gas in the inspection well.

[0014] Furthermore, the specific operation steps of step S5 are: analyzing the detection of tracer gas in the vicinity of the tracer gas injection point and in the upstream and downstream inspection wells; when tracer gas is detected in all inspection wells located in the same rainwater pipe or sewage pipe, these inspection wells located in the same rainwater pipe or sewage pipe are all connected; when one of two adjacent inspection wells located in the same rainwater pipe or sewage pipe does not detect tracer gas, while the other inspection well detects tracer gas, the pipelines between the two adjacent inspection wells are not connected, and there is a mixed connection point between the rainwater pipe and the sewage pipe.

[0015] The beneficial effects of the method of the present invention based on rapid detection of VOCs tracer gas to identify mixed and wrong connections in urban pipe networks are as follows: By detecting VOCs (volatile organic compounds), the present invention can quickly and accurately find tracer gases. By analyzing the detection and concentration changes of tracer gases in each inspection well, the connectivity of pipelines can be analyzed and the locations of mixed connections between rainwater pipes and sewage pipes can be located, providing scientific support for pipe network management. The present invention injects volatile, non-toxic, low-cost, and low-background tracer gases such as ethanol into the injection point within a short period of time. Using TOF-MS high-resolution detection technology, VOCs detection can be rapidly carried out in all inspection wells in the surrounding and upstream and downstream areas. By detecting and analyzing the tracer gas, the connectivity of the pipeline can be quickly determined, effectively improving detection efficiency. In gas tracing, the present invention selects a gas with less obvious local characteristics as the tracer gas, thereby preventing the tracer gas from interfering with the results and improving the accuracy of detection and identification. At the same time, through gas diffusion model calculation, the specific point of mixed and wrong connections can be accurately identified based on the concentration changes of the tracer gas, further improving the accuracy of mixed and wrong connection identification. In actual application, the present invention does not require construction and installation of equipment, and can flexibly monitor each inspection well along the pipeline according to the pipeline network route map. It can not only be used to check the mixed connection points of rainwater and sewage pipes, but also can be used to trace the source of pipeline pollution, external water intrusion and other problems. It has the advantages of strong economy, wide application range and low detection and identification cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 — is a distribution relationship diagram of rainwater pipes and sewage pipes in the target area in Example 1; Figure 2 — is the TOF-MS spectrum of the sewage pipe and stormwater pipe in Example 1; Figure 3 — is a distribution diagram of the tracer gas injection points and each inspection well in Example 1; Figure 4 — is a diagram showing the detection status of tracer gas in each inspection well in Example 1; Figure 5 —It is the rain-pollution mixing error contact bitmap based on tracer gas identification. DETAILED DESCRIPTION

[0017] The present invention provides a method for identifying mixed or misconnected urban pipe networks based on rapid detection of VOCs tracer gas, comprising the following steps: S1. Sort out the basic situation of the pipelines in the target area, analyze the distribution relationship between the rainwater pipes and sewage pipes in the target area, and select representative inspection wells in the target area as the monitoring points; S2. Based on the PTR-TOF-MS high-resolution detection technology, a collection tube was used to collect and analyze VOCs in the rainwater pipe and sewage pipe. The collected gas was sampled into a proton transfer reaction time-of-flight mass spectrometer for VOCs detection. According to the detection results of the TOF-MS spectrum of VOCs in the rainwater pipe and sewage pipe, a non-toxic, volatile gas with no obvious background characteristics was selected as the tracer gas; the conditions for VOCs gas detection and analysis using PTR-TOF-MS were: the mass scanning range was 1-500 amu, and the instrument vacuum was less than or equal to 10 -4 Pa, drift tube pressure 50-500 Pa. The background characteristics are not obvious when the response value of the tracer gas in the VOCs spectrum in the rainwater pipe and sewage pipe is less than one thousandth of the highest response value; S3. Select a tracer gas injection point and inject the tracer gas into the pipeline; the tracer gas injection point is selected at the upstream inspection well of the pipeline.

[0018] S4. Based on the tracer gas injection point, use a collection tube to collect VOCs in representative inspection wells around the tracer gas injection point and upstream and downstream. Based on the PTR-TOF-MS high-resolution detection technology, the collected gas is sampled into a proton transfer reaction time-of-flight mass spectrometer for VOCs detection and analysis to detect whether there is tracer gas in the inspection well. Representative inspection wells are inspection wells at key pipeline nodes or pipeline starting wells. S5. Analyze the detection of tracer gas around the tracer gas injection point and in the upstream and downstream inspection wells. If tracer gas is detected in all inspection wells located in the same stormwater pipe or sewage pipe, then these inspection wells located in the same stormwater pipe or sewage pipe are connected. If tracer gas is not detected in one of two adjacent inspection wells located in the same stormwater pipe or sewage pipe, while tracer gas is detected in the other inspection well, then the pipelines between the two adjacent inspection wells are disconnected, indicating that a stormwater pipe and sewage pipe are mixed up at a wrong connection point. The following is a clear and complete description of the technical solutions of the present invention by way of embodiments in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0019] Example 1

[0020] In a target area, there is a misconnection of rainwater and sewage pipes, and it is necessary to identify the points where the rainwater pipes and sewage pipes are misconnected. This embodiment uses a method of the present invention based on VOCs tracer gas rapid detection to identify misconnections in urban pipe networks to identify the points where the rainwater and sewage pipes are misconnected, including the following steps: S1. Sort out the basic situation of pipelines in the target area and analyze the distribution relationship between rainwater pipes and sewage pipes in the target area (such as Figure 1 shown); by Figure 1 It can be seen that there are three pipelines in the target area, one is a sewage pipe (purple line), and there are two intersecting rainwater pipes (rainwater pipe 1 and rainwater pipe 2, blue lines), and there is an intersection between the sewage pipe and rainwater pipe 1; S2. Based on TOF-MS high-resolution detection technology, a gas sampling tube was used to sample and analyze VOCs in the rainwater pipe and sewage pipe. The collected gas was injected into a proton transfer reaction time-of-flight mass spectrometer for VOCs detection, and TOF-MS spectra of VOCs in the rainwater pipe and sewage pipe were obtained. The conditions for VOCs gas detection and analysis using PTR-TOF-MS were: mass scanning range of 300 amu, instrument vacuum of 10 -4Pa, the mass spectrometry background spectrum is mainly water peak, the water vapor injection volume is 1-50 mL / min, and the drift tube pressure is 250 Pa; According to the TOF-MS spectra of VOCs in rainwater pipes and sewage pipes (such as Figure 2 Based on the test results shown in the figure, a non-toxic, volatile gas with no obvious background characteristics is selected as the tracer gas; Figure 2 It can be seen that the background characteristics of ethanol (M / Z 47) in the pipeline are not obvious (the response value corresponding to ethanol is less than one thousandth of the maximum response value. The response value is also the ion signal intensity, which is the value corresponding to the vertical axis of the TOF-MS spectrum). Therefore, ethanol can be selected as the tracer gas. S3. Select the tracer gas injection point in the upstream area of the sewage pipe (such as Figure 3 In the figure, blue is the rainwater pipe and purple is the sewage pipe), and the tracer gas is injected into the sewage pipe; S4. Based on the tracer gas injection point, VOCs are sampled in representative inspection wells around the tracer gas injection point and upstream and downstream using a collection tube. Based on the PTR-TOF-MS high-resolution detection technology, the collected gas is sampled into a proton transfer reaction time-of-flight mass spectrometer for VOCs detection and analysis. The detection and analysis conditions are the same as S2, and the presence of tracer gas in the inspection well is detected. In this embodiment, sewage well A located above rainwater pipe 1 and sewage wells B, C, and D located below rainwater pipe 1 are selected from the sewage pipeline. Rainwater well A is selected from the rainwater pipeline 1. Rainwater well B at the intersection of rainwater pipe 1 and rainwater pipe 2, and rainwater wells C, D, and E located downstream of rainwater well B on the rainwater pipeline 2 are selected. S5. Analyze the detection of tracer gas around the injection point and in the upstream and downstream inspection wells (such as Figure 4 ),Depend on Figure 4 It can be seen that ethanol (tracer gas) was detected in sewage wells AD, indicating that sewage wells AD in the sewage pipe are connected; On rainwater pipe 1, ethanol (tracer gas) was detected in rainwater well A, but not in rainwater well B. This indicates that one of the two adjacent rainwater wells on rainwater pipe 1 did not detect tracer gas, while the other (rainwater well A) did. This indicates that the pipes between these two adjacent inspection wells (rainwater well A and rainwater well B) are disconnected, indicating that the rainwater pipe and sewage pipe are mixed at a wrong connection point. Since the sewage pipe and rainwater pipe 1 intersect, the intersection of the sewage pipe and rainwater pipe 1 further identifies the presence of a mixed connection between the sewage pipe and rainwater pipe 1. Moreover, since rainwater well B is the intersection of rainwater pipe 1 and rainwater pipe 2, it detected tracer gas there, but rainwater well A in rainwater pipe 1 did not, indicating that rainwater pipe 1 and rainwater pipe 2 are disconnected. On rainwater pipe 2, no ethanol (tracer gas) was detected in rainwater well BD, but ethanol (tracer gas) was detected in rainwater well E adjacent to rainwater well D. This shows that on rainwater pipe 2, one of the two adjacent rainwater wells (rainwater well D) did not detect tracer gas, while the other inspection well (rainwater well E) detected tracer gas, indicating that there is a mixed connection point between the rainwater pipe and the sewage pipe in the pipeline between the two adjacent inspection wells (rainwater well D and rainwater well E).

[0021] Therefore, by adopting the method of this embodiment, the pipe network problems existing in the area can be found out (such as Figure 5 As shown): 1. The mixed connection point of the rainwater pipe and the sewage pipe is between rainwater well A and rainwater well B and is located at the intersection of rainwater pipe 1 and sewage pipe; 2. Rainwater pipe 1 and rainwater pipe 2 are not connected; 3. The mixed connection point of the rainwater pipe and the sewage pipe is between rainwater well D and rainwater well E, and rainwater pipe 1 and rainwater pipe 2 are not connected. After on-site investigation, it was found that there was indeed a mixed connection phenomenon of rainwater pipes and sewage pipes between rainwater well A and rainwater well B, and between rainwater well D and rainwater well E, and rainwater pipe 1 and rainwater pipe 2 were not connected, indicating that the present invention accurately found the rainwater and sewage mixing points in a relatively short time by adopting VOCs detection and analysis and gas tracing methods, and effectively solved the problem of troubleshooting the mixed connection of rainwater pipes and sewage pipes in this area.

[0022] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for identifying mixed and wrong connections in urban pipe networks based on rapid detection of VOCs tracer gas, characterized in that: The following steps are involved: S1. Sort out the basic situation of pipelines in the target area and analyze the distribution relationship between rainwater pipes and sewage pipes in the target area; S2. Conduct gas sampling and analysis of VOCs in rainwater pipes and sewage pipes, detect the VOCs composition in the rainwater pipes and sewage pipes, obtain VOCs spectra in the rainwater pipes and sewage pipes, and select non-toxic, volatile gases with no obvious background characteristics as tracer gases based on the detection results of the VOCs spectra in the rainwater pipes and sewage pipes; S3. Select a tracer gas injection point and inject the tracer gas into the pipeline; S4. Based on the tracer gas injection point, perform gas sampling and detection of VOCs in representative inspection wells around the tracer gas injection point and upstream and downstream to detect whether there is tracer gas; S5. Analyze the detection of tracer gas around the tracer gas injection point and in the upstream and downstream inspection wells to quickly determine the connectivity between the pipelines and the mixed connection points of rainwater pipes and sewage pipes.

2. A method for identifying mixed and wrong connections in urban pipe networks based on rapid detection of VOCs tracer gas according to claim 1, characterized in that: The representative inspection well is a pipeline key node inspection well or a pipeline starting well.

3. The method for identifying mixed and wrong connections in urban pipe networks based on rapid detection of VOCs tracer gas according to claim 1, characterized in that: The specific operation steps of step S2 are: after collecting VOCs gas from the rainwater pipe and the sewage pipe with a collection tube, the VOCs gas is detected and analyzed based on the PTR-TOF-MS high-resolution detection technology to form a TOF-MS spectrum of VOCs in the rainwater pipe and the sewage pipe, and TOF-MS spectrum data of VOCs in the rainwater pipe and the sewage pipe is obtained. According to the spectrum data, a non-toxic, volatile gas with no obvious background characteristics is selected as a tracer gas.

4. A method for identifying mixed and wrong connections in urban pipe networks based on rapid detection of VOCs tracer gas as claimed in claim 3, characterized in that: The conditions for VOCs gas detection and analysis using PTR-TOF-MS are: mass scanning range 1-500 amu, instrument vacuum degree less than or equal to 10 -4 Pa, drift tube pressure 50-500Pa.

5. The method for identifying mixed and wrong connections in urban pipe networks based on rapid detection of VOCs tracer gas according to claim 1, characterized in that: The background characteristics of the tracer gas in step S2 are not obvious, which means that in the VOCs spectrum in the rainwater pipe and the sewage pipe, the response value corresponding to the tracer gas is less than one thousandth of the maximum response value.

6. The method for identifying mixed and wrong connections in urban pipe networks based on rapid detection of VOCs tracer gas according to claim 1, characterized in that: In step S3, the tracer gas injection point is selected as the upstream inspection well of the pipeline.

7. The method for identifying mixed or incorrect connections in urban pipe networks based on rapid detection of VOCs tracer gas according to claim 1, characterized in that: The specific operation steps of step S4 are: according to the tracer gas injection point, use a collection tube to collect VOCs in the vicinity of the tracer gas injection point and in representative inspection wells upstream and downstream, and detect and analyze the VOCs gas based on the PTR-TOF-MS high-resolution detection technology to detect whether there is tracer gas in the inspection well.

8. The method for identifying mixed or incorrect connections in urban pipe networks based on rapid detection of VOCs tracer gas according to claim 1, characterized in that: The specific operation steps of step S5 are: analyzing the detection of tracer gas around the tracer gas injection point and in the upstream and downstream inspection wells. When tracer gas is detected in all inspection wells located in the same rainwater pipe or sewage pipe, these inspection wells located in the same rainwater pipe or sewage pipe are all connected; when one of two adjacent inspection wells located in the same rainwater pipe or sewage pipe does not detect tracer gas, while the other inspection well detects tracer gas, the pipelines between the two adjacent inspection wells are not connected, and there is a mixed connection point between the rainwater pipe and the sewage pipe.

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