A method of estimating the rate of water ingress into a sewer pipe

Abstract

The application discloses a method for estimating the water mixing rate outside a sewage pipeline, and belongs to the technical field of municipal sewage pipeline network water environment monitoring. The method collects actual treatment water quantity data and influent pollutant concentration data of a target sewage treatment plant, obtains preset domestic sewage pollutant concentration data and preset external water pollutant concentration data, constructs a water quantity balance and pollutant balance equation set and completes solving, obtains domestic sewage water quantity and external water mixing water quantity, obtains the water mixing rate outside the sewage pipeline through proportional calculation, can also obtain the average external water mixing rate based on the calculation results of multiple types of pollutants, and completes the external water mixing degree grading of the pipeline network. The method is suitable for measuring and calculating the leakage underground water or rainwater mixing amount of the urban sewage pipeline network, can complete the measurement and calculation by using the conventional online monitoring data of the plant area, and can improve the reliability of the final mixing rate value through the joint calculation of multiple pollutants.

Description

Technical Field

[0001] This invention belongs to the field of municipal sewage pipe network water environment monitoring technology, specifically involving the quantitative estimation of the amount and proportion of external water mixed into urban sewage pipes. Background Technology

[0002] Wastewater pipe networks are a crucial component of municipal infrastructure, responsible for transporting urban wastewater and playing a vital role in maintaining public environmental health. In most Chinese cities, wastewater pipe networks have been in service for a long time, making upgrades and renovations difficult. Pipeline damage and leakage are common problems, and external water bodies can easily contaminate the sewage network. Large amounts of external water entering the network increase its water transport load, leading to a decrease in the concentration of pollutants in the influent to wastewater treatment plants. This increases the operating costs of wastewater transportation and treatment, disrupts the normal operation of wastewater treatment plants, and in severe cases, can cause wastewater overflows, adversely affecting the surrounding water environment.

[0003] Currently, the investigation of external water in the pipe network typically requires the deployment of specialized testing equipment, pipe point mapping, and on-site assessment by professionals, resulting in high initial investment costs. Urban sewage pipe networks cover a wide area, and conducting a comprehensive, segment-by-segment investigation across the entire region is labor-intensive and time-consuming. It is difficult to quickly identify pipe sections with significant external water contamination, failing to provide clear guidance for subsequent detailed investigations and hindering municipal management departments from efficiently carrying out pipe network operation and maintenance and external water treatment. Summary of the Invention

[0004] The purpose of this invention is to provide a method for estimating the rate of external water mixing in sewage pipelines, in order to solve the problems of high investment costs, long operation cycles, and difficulty in quickly and quantitatively assessing the degree of external water mixing in existing pipeline networks.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for estimating the rate of external water mixing in sewage pipelines includes the following steps:

[0007] Obtain actual treated water volume data and influent pollutant concentration data of the target wastewater treatment plant;

[0008] Acquire preset data on pollutant concentrations in domestic sewage and external water.

[0009] Based on the actual treated water volume data, influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data, a set of water volume balance and pollutant balance equations is established.

[0010] The water balance and pollutant balance equations are solved to obtain the volume of domestic sewage and the volume of mixed external water.

[0011] The external water mixing rate is calculated based on the ratio of the amount of water mixed in with the amount of domestic sewage.

[0012] In one possible implementation, the steps for obtaining actual treated water volume data and influent pollutant concentration data of the target wastewater treatment plant include:

[0013] Collect the average daily treated water volume data of the target wastewater treatment plant and generate actual treated water volume data;

[0014] Collect concentration data of various pollutants at the inlet of the target wastewater treatment plant to generate influent pollutant concentration data.

[0015] In one possible implementation, the steps for obtaining preset domestic sewage pollutant concentration data and preset external water pollutant concentration data include:

[0016] Based on the National Pollution Source Census Domestic Source Pollution Discharge Coefficient Manual, extract the pollutant concentration data of domestic sewage in the corresponding areas;

[0017] Collect water quality data of water bodies surrounding the target wastewater treatment plant to generate external water pollutant concentration data.

[0018] In one possible implementation, the steps of establishing a set of water balance and pollutant balance equations based on the actual treated water volume data, influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data include:

[0019] Based on the actual treated water volume data, a water balance equation is established that the sum of domestic sewage volume and external water mixed in is equal to the actual treated water volume.

[0020] Based on the influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data, a pollutant balance equation is established in which the sum of the total amount of domestic sewage pollutants and the total amount of external water pollutants equals the total amount of influent pollutants of the sewage treatment plant.

[0021] The water balance equation and the pollutant balance equation are integrated to form a set of water balance and pollutant balance equations.

[0022] In one possible implementation, the steps of solving the water balance and pollutant balance equations to obtain the volume of domestic sewage and the volume of mixed external water include:

[0023] The water balance equation is transformed into an expression where the amount of external water mixed in equals the actual amount of treated water minus the amount of domestic sewage.

[0024] Substitute the expression into the pollutant balance equation and solve the linear equation in one variable to obtain the amount of domestic sewage.

[0025] The amount of external water mixed in is obtained by calculating and processing the amount of domestic sewage and the expression.

[0026] In one possible implementation, the step of calculating the external water mixing rate based on the ratio of the external water mixing volume to the domestic sewage volume includes:

[0027] Calculate the ratio of the amount of external water mixed in to the amount of domestic sewage;

[0028] Convert the ratio to a percentage to generate the sewage pipe external water mixing rate.

[0029] In one possible implementation, the steps of collecting multiple pollutant concentration data at the inlet of the target wastewater treatment plant and generating influent pollutant concentration data include:

[0030] Collect chemical oxygen demand (COD) concentration data at the inlet of the target wastewater treatment plant;

[0031] Collect biochemical oxygen demand (BOD) concentration data at the inlet of the target wastewater treatment plant;

[0032] Collect ammonia nitrogen concentration data at the inlet of the target wastewater treatment plant;

[0033] Collect total phosphorus concentration data at the inlet of the target wastewater treatment plant;

[0034] By integrating the chemical oxygen demand (COD) concentration data, biochemical oxygen demand (BOD) concentration data, ammonia nitrogen concentration data, and total phosphorus concentration data, influent pollutant concentration data is generated.

[0035] One possible implementation also includes:

[0036] Statistical analysis was performed on the external water mixing rates corresponding to various pollutants to generate the average external water mixing rate.

[0037] The degree of external water mixing in the pipeline network is classified based on the average external water mixing rate to generate an external water mixing risk level result.

[0038] Compared with existing technologies, the advantages of this invention are as follows: Compared with the external water investigation method that relies on on-site specialized equipment detection and segment-by-segment pipeline mapping, this method for estimating the external water mixing rate in sewage pipelines is based on the actual treated water volume and influent pollutant concentration data of sewage treatment plants. It constructs a set of water balance and pollutant balance equations by combining preset parameters for domestic sewage and external water pollutant concentrations. By solving these equations, the volume of domestic sewage and the volume of external water mixed in are obtained, and then the external water mixing rate is calculated. The entire process does not require a large investment in on-site surveying and equipment costs, which can shorten the assessment cycle and quickly complete the preliminary screening of the degree of external water mixing in the target area's sewage pipelines.

[0039] Compared to methods that estimate based on a single pollutant indicator, this invention can calculate the corresponding external water mixing rate by combining multiple influent pollutant concentration data, and then obtain the average external water mixing rate through statistical analysis. Furthermore, it can be used to classify the degree of external water mixing. This multi-indicator calculation method reduces the bias caused by fluctuations in a single indicator, enhances the reference value of the estimation results, helps managers quickly identify areas with significant external water mixing impacts, and also facilitates refined investigation and pipeline management. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a flowchart illustrating the method for estimating the external water mixing rate in sewage pipelines according to an embodiment of the present invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some 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 scope of protection of this application.

[0043] Example:

[0044] It should be noted that the terms "comprising" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0045] See Figure 1 This embodiment of a method for estimating the mixing rate of external water in sewage pipelines includes the following steps:

[0046] Step 101: Obtain the actual treated water volume data and influent pollutant concentration data of the target wastewater treatment plant.

[0047] Specifically, the actual treated water volume data can be statistical data on the actual wastewater flow rate treated by the wastewater treatment plant; the influent pollutant concentration data can be the concentration detection data of various pollutants at the inlet of the wastewater treatment plant.

[0048] The steps for obtaining actual treated water volume data and influent pollutant concentration data of the target wastewater treatment plant include:

[0049] Collect the average daily treated water volume data of the target wastewater treatment plant and generate actual treated water volume data;

[0050] Collect concentration data of various pollutants at the inlet of the target wastewater treatment plant to generate influent pollutant concentration data.

[0051] Specifically, the daily average treated water volume data can be the daily average statistical data of the wastewater treatment plant's daily treated water volume; the multiple pollutant concentration data can be the set of concentration detection data of different types of pollutants in the inlet.

[0052] Furthermore, the steps for collecting multiple pollutant concentration data at the inlet of the target wastewater treatment plant and generating influent pollutant concentration data include:

[0053] Collect chemical oxygen demand (COD) concentration data at the inlet of the target wastewater treatment plant;

[0054] Collect biochemical oxygen demand (BOD) concentration data at the inlet of the target wastewater treatment plant;

[0055] Collect ammonia nitrogen concentration data at the inlet of the target wastewater treatment plant;

[0056] Collect total phosphorus concentration data at the inlet of the target wastewater treatment plant;

[0057] By integrating the chemical oxygen demand (COD) concentration data, biochemical oxygen demand (BOD) concentration data, ammonia nitrogen concentration data, and total phosphorus concentration data, influent pollutant concentration data is generated.

[0058] Specifically, chemical oxygen demand (COD) concentration data can be COD index detection data that characterizes the degree of organic pollution in water bodies; biochemical oxygen demand (BOD) concentration data can be BOD index detection data that characterizes the content of biodegradable organic matter; ammonia nitrogen concentration data can be detection data that characterizes the content of ammonia nitrogen nutrients in water bodies; and total phosphorus concentration data can be detection data that characterizes the total amount of phosphorus nutrients in water bodies.

[0059] Step 102: Obtain preset data on pollutant concentrations in domestic sewage and preset data on pollutant concentrations in external water.

[0060] Specifically, the pollutant concentration data for domestic sewage can be reference values ​​for typical pollutant concentrations in domestic sewage within the municipal pipe network, while the pollutant concentration data for external water can be pollutant concentration data for external water bodies that have entered the pipe network.

[0061] The steps for obtaining preset domestic sewage pollutant concentration data and preset external water pollutant concentration data include:

[0062] Based on the National Pollution Source Census Domestic Source Pollution Discharge Coefficient Manual, extract the pollutant concentration data of domestic sewage in the corresponding areas;

[0063] Collect water quality data of water bodies surrounding the target wastewater treatment plant to generate external water pollutant concentration data.

[0064] Specifically, the National Pollution Source Census Domestic Source Pollution Generation and Discharge Coefficient Manual can be an authoritative reference manual officially released and recording the generation and discharge coefficients of domestic pollutants in various regions; the corresponding region can be a geographical area that is consistent with the administrative division of the service area of ​​the target sewage treatment plant; the surrounding water bodies can be surface water bodies such as rivers and lakes within the service area of ​​the sewage treatment plant that may be mixed in through pipeline defects; and the water quality data can be the detection data of the concentration of various pollutants in the surrounding water bodies.

[0065] Step 103: Based on the actual treated water volume data, influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data, establish a set of water volume balance and pollutant balance equations.

[0066] Specifically, water balance can be a conservation relationship where the total amount of water entering the wastewater treatment plant is equal to the sum of the amount of domestic sewage and the amount of water mixed with external water; pollutant balance can be a conservation relationship where the total amount of pollutants entering the wastewater treatment plant is equal to the sum of the total amount of pollutants in domestic sewage and the total amount of pollutants in external water; the water balance and pollutant balance equations can be a system of two linear equations in two variables, which is formed by combining the water balance equation and the pollutant balance equation.

[0067] The steps for establishing a set of water balance and pollutant balance equations based on the actual treated water volume data, influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data include:

[0068] Based on the actual treated water volume data, a water balance equation is established that the sum of domestic sewage volume and external water mixed in is equal to the actual treated water volume.

[0069] Based on the influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data, a pollutant balance equation is established in which the sum of the total amount of domestic sewage pollutants and the total amount of external water pollutants equals the total amount of influent pollutants of the sewage treatment plant.

[0070] The water balance equation and the pollutant balance equation are integrated to form a set of water balance and pollutant balance equations.

[0071] Specifically, the water balance equation can be a linear equation describing the conservation relationship between the volume of domestic sewage, the volume of external water mixed in, and the actual volume of treated water; the pollutant balance equation can be a linear equation describing the conservation relationship between the total amount of pollutants in domestic sewage, the total amount of pollutants in external water, and the total amount of pollutants in influent; the total amount of pollutants in domestic sewage can be the pollutant mass flow rate obtained by multiplying the volume of domestic sewage by the concentration of pollutants in domestic sewage; the total amount of pollutants in external water can be the pollutant mass flow rate obtained by multiplying the volume of external water mixed in by the concentration of pollutants in external water; and the total amount of pollutants in influent can be the pollutant mass flow rate obtained by multiplying the actual volume of treated water by the concentration of pollutants in influent.

[0072] For example, a water balance equation is established where the total water volume equals the sum of the volume of domestic sewage and the volume of water mixed with external water: ;

[0073] In the formula, This represents the volume of raw domestic sewage in the pipe network corresponding to the i-th type of pollutant. This represents the amount of water mixed into the pipeline network corresponding to the i-th type of pollutant;

[0074] For pollutant type i, construct the total pollutant balance relationship: ;

[0075] In the formula, This represents the total daily mass of pollutants of type i carried by domestic sewage. This represents the total daily mass of pollutants of type i carried by external water. This represents the preset concentration of pollutants in domestic sewage corresponding to the i-th type of pollutant. This represents the preset concentration of external water pollutants corresponding to the i-th type of pollutant. This represents the concentration of pollutants in the wastewater treatment plant corresponding to the i-th type of pollutant.

[0076] Step 104: Solve the water balance and pollutant balance equations to obtain the amount of domestic sewage and the amount of water mixed with external water.

[0077] Specifically, the volume of domestic sewage can be the flow rate of domestic sewage discharged into the sewage treatment plant from the municipal pipe network; the volume of external water mixed in can be the flow rate of external water bodies mixed into the pipe network through pipe defects.

[0078] The steps of solving the water balance and pollutant balance equations to obtain the volume of domestic sewage and the volume of mixed external water include:

[0079] The water balance equation is transformed into an expression where the amount of external water mixed in equals the actual amount of treated water minus the amount of domestic sewage.

[0080] Substitute the expression into the pollutant balance equation and solve the linear equation in one variable to obtain the amount of domestic sewage.

[0081] The amount of external water mixed in is obtained by calculating and processing the amount of domestic sewage and the expression.

[0082] Specifically, the expression can be an algebraic relationship that expresses the amount of external water mixed in using the actual amount of treated water and the amount of domestic sewage; substitution can be an algebraic operation that replaces the variable expression in one equation with that in another equation; solving a linear equation in one variable can be the calculation process of solving a linear equation containing only one unknown.

[0083] For example, by transforming the water balance equation, we obtain the substitution expression for the amount of external water mixed in corresponding to the i-th type of pollutant: ;

[0084] After removing the common denominator, we obtain the pollutant balance equations used to solve the water quantity parameters simultaneously: ;

[0085] Step 105: Calculate the ratio of the amount of external water mixed in with the amount of domestic sewage to generate the external water mixing rate in the sewage pipeline.

[0086] Specifically, the proportional calculation process can be a calculation of the ratio of the amount of external water mixed in to the amount of domestic sewage; the external water mixing rate in sewage pipes can be a percentage indicator that characterizes the degree of external water mixing.

[0087] The step of calculating the external water mixing rate of the sewage pipe based on the ratio of the external water mixing volume to the domestic sewage volume includes:

[0088] Calculate the ratio of the amount of external water mixed in to the amount of domestic sewage;

[0089] Convert the ratio to a percentage to generate the sewage pipe external water mixing rate.

[0090] Specifically, the ratio can be a dimensionless value obtained by dividing the amount of external water mixed in by the amount of domestic sewage; the percentage form can be a form in which the ratio is multiplied by 100 and then a percentage sign is added.

[0091] For example, by substituting the water quantity parameters obtained from the solution, the external water mixing rate corresponding to the i-th type of pollutant is calculated:

[0092] In the formula, This represents the amount of external water mixed in corresponding to the i-th type of pollutant. This represents the volume of domestic sewage corresponding to the i-th type of pollutant.

[0093] In one embodiment, it further includes:

[0094] Statistical analysis was performed on the external water mixing rates corresponding to various pollutants to generate the average external water mixing rate.

[0095] The degree of external water mixing in the pipeline network is classified based on the average external water mixing rate to generate an external water mixing risk level result.

[0096] Specifically, statistical analysis can be a process of summarizing and statistically analyzing the external water mixing rates calculated separately for multiple pollutants; the average external water mixing rate can be the arithmetic mean of the external water mixing rates corresponding to multiple pollutants; the classification of the degree of external water mixing in the pipe network can be a process of dividing different risk levels according to the numerical range of the average external water mixing rate; the result of the external water mixing risk level can be a classification evaluation conclusion characterizing the severity of external water mixing in the pipe network.

[0097] A wastewater treatment plant in a certain district of a city in Guangdong Province was selected as a case study. The plant has a designed treatment capacity of 410,000 tons per day and an average daily treatment volume of 380,000 tons per day. The parameter values ​​were determined with reference to the Second National Pollution Source Census's Manual of Verification Coefficients for Domestic Wastewater Production and Discharge. The baseline concentrations of various pollutants in domestic wastewater were determined to be: Chemical Oxygen Demand (COD) 300 mg / L, Biochemical Oxygen Demand (BOD) 135 mg / L, Ammonia Nitrogen 29.5 mg / L, and Total Phosphorus 4.14 mg / L. The corresponding parameter information is summarized in Table 1.

[0098] Table 1. Average Concentration of Domestic Sewage in a City, Guangdong Province

[0099] Table 1 records the average concentration data of domestic sewage in a certain city in Guangdong Province. Subsequently, the calculation formula corresponding to the external water mixing rate is used to perform calculations to complete the calculation of the external water mixing rate of the sewage treatment plant in a certain district of a certain city in Guangdong Province. The final calculation results are summarized in Table 2.

[0100] Table 2. Statistical Table of Average External Water Contamination in Relevant Wastewater Treatment Plants in a Certain District of a City, Guangdong Province in Recent Years

[0101] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0102] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for estimating the external water mixing rate in sewage pipelines, characterized in that, Includes the following steps: Obtain actual treated water volume data and influent pollutant concentration data of the target wastewater treatment plant; Acquire preset data on pollutant concentrations in domestic sewage and external water. Based on the actual treated water volume data, influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data, a set of water volume balance and pollutant balance equations is established. The water balance and pollutant balance equations are solved to obtain the volume of domestic sewage and the volume of mixed external water. The external water mixing rate is calculated based on the ratio of the amount of water mixed in with the amount of domestic sewage.

2. The method for estimating the external water mixing rate in sewage pipelines according to claim 1, characterized in that, The steps to obtain actual treated water volume data and influent pollutant concentration data of the target wastewater treatment plant include: Collect the average daily treated water volume data of the target wastewater treatment plant and generate actual treated water volume data; Collect concentration data of various pollutants at the inlet of the target wastewater treatment plant to generate influent pollutant concentration data.

3. The method for estimating the external water mixing rate in sewage pipelines according to claim 1, characterized in that, The steps for obtaining preset domestic sewage pollutant concentration data and preset external water pollutant concentration data include: Based on the National Pollution Source Census Domestic Source Pollution Discharge Coefficient Manual, extract the pollutant concentration data of domestic sewage in the corresponding areas; Collect water quality data of water bodies surrounding the target wastewater treatment plant to generate external water pollutant concentration data.

4. The method for estimating the external water mixing rate in sewage pipelines according to claim 1, characterized in that, The steps for establishing a set of water balance and pollutant balance equations based on the actual treated water volume data, influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data include: Based on the actual treated water volume data, a water balance equation is established that the sum of domestic sewage volume and external water mixed in is equal to the actual treated water volume. Based on the influent pollutant concentration data, domestic sewage pollutant concentration data, and external water pollutant concentration data, a pollutant balance equation is established in which the sum of the total amount of domestic sewage pollutants and the total amount of external water pollutants equals the total amount of influent pollutants of the sewage treatment plant. The water balance equation and the pollutant balance equation are integrated to form a set of water balance and pollutant balance equations.

5. The method for estimating the external water mixing rate in sewage pipelines according to claim 4, characterized in that, The steps for solving the water balance and pollutant balance equations to obtain the volume of domestic sewage and the volume of mixed external water include: The water balance equation is transformed into an expression where the amount of external water mixed in equals the actual amount of treated water minus the amount of domestic sewage. Substitute the expression into the pollutant balance equation and solve the linear equation in one variable to obtain the amount of domestic sewage. The amount of external water mixed in is obtained by calculating and processing the amount of domestic sewage and the expression.

6. The method for estimating the external water mixing rate in sewage pipelines according to claim 1, characterized in that, The steps for calculating the external water mixing rate of sewage pipes based on the ratio of the external water mixing volume and the domestic sewage volume include: Calculate the ratio of the amount of external water mixed in to the amount of domestic sewage; Convert the ratio to a percentage to generate the sewage pipe external water mixing rate.

7. The method for estimating the external water mixing rate in sewage pipelines according to claim 2, characterized in that, The steps for collecting multiple pollutant concentration data at the inlet of the target wastewater treatment plant and generating influent pollutant concentration data include: Collect chemical oxygen demand (COD) concentration data at the inlet of the target wastewater treatment plant; Collect biochemical oxygen demand (BOD) concentration data at the inlet of the target wastewater treatment plant; Collect ammonia nitrogen concentration data at the inlet of the target wastewater treatment plant; Collect total phosphorus concentration data at the inlet of the target wastewater treatment plant; By integrating the chemical oxygen demand (COD) concentration data, biochemical oxygen demand (BOD) concentration data, ammonia nitrogen concentration data, and total phosphorus concentration data, influent pollutant concentration data is generated.

8. The method for estimating the external water mixing rate in sewage pipelines according to claim 1, characterized in that, Also includes: Statistical analysis was performed on the external water mixing rates corresponding to various pollutants to generate the average external water mixing rate. The degree of external water mixing in the pipeline network is classified based on the average external water mixing rate to generate an external water mixing risk level result.

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