Urban drainage system carbon emission reduction accounting method suitable for pipeline repair scene

Abstract

The invention discloses an urban drainage system carbon emission reduction accounting method suitable for a pipeline repair scene, and the method comprises the following steps: (1) collecting water supply data, a drainage water quality background value and the operation data of a sewage treatment plant in an accounting region, and calculating and evaluating the pipe network defects of an urban drainage system; (2) related carbon footprint evaluation parameters in the urban drainage system are collected, and historical carbon emissions of a drainage pipeline, a sewage treatment plant and a receiving water body in the urban drainage system are calculated; (3) setting a pipe network repair scene according to the control targets of the sewage collection rate and the external water invasion rate; and (4) inputting the carbon footprint evaluation parameters of the urban drainage system into the Monte Carlo simulation model to obtain dynamic prediction results of carbon emission of the urban drainage system under different scenes. According to the method, the influence degree of different pipe network defects on carbon emission in sewage / rainwater collection, conveying, treatment and emission scenes of the drainage system is rapidly determined, and the urban drainage system is assisted to achieve the purpose of carbon neutralization.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection management and control, and specifically relates to a carbon emission reduction accounting method for an urban drainage system suitable for a pipeline repair scenario. Background Art

[0004] At present, no study has evaluated the impact of drainage network defects on the carbon emissions of urban drainage systems. Therefore, it is urgent to develop a carbon reduction prediction method for urban drainage systems based on pipeline repair scenarios to promote the alignment of urban infrastructure renewal planning with urban carbon reduction planning.

[0005] CN 115392757A discloses a method and device for quantitatively evaluating carbon emissions of urban sewage treatment facilities. The method determines the carbon emissions of the drainage network and sewage treatment plants in the urban drainage system by collecting the original data of the network and the academician data of the sewage treatment plant. However, the method does not consider the impact of the defects of the urban drainage network on the carbon emissions of the drainage network and sewage treatment plants. Therefore, the method may not be accurate in evaluating the carbon emission reduction potential of urban sewage treatment facilities.

[0006] CN 115641026A discloses a method for calculating carbon emissions from a sewage treatment plant, which evaluates the impact of different emission reduction technologies on the carbon emission potential of the sewage treatment plant through a life cycle assessment method. However, the carbon footprint assessment parameters used in this method are mainly derived from various data lists, and the data quality is difficult to guarantee and has great uncertainty. Summary of the invention

[0007] The purpose of the present invention is to provide a method for calculating carbon emission reductions of urban drainage systems in a pipeline repair scenario based on Monte Carlo simulation, which solves the problem that the existing carbon emission reduction calculation results of drainage systems do not take into account the impact of defects in urban drainage pipe networks.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A carbon emission reduction accounting method for an urban drainage system applicable to a pipeline repair scenario comprises the following steps:

[0010] S1- Collect water supply data, drainage water quality background value, pollution coefficient and operation data of sewage treatment plants in the accounting area, calculate the direct discharge of sewage and external water intrusion of urban drainage system to evaluate the defects of urban drainage system pipeline network; S2- Collect relevant carbon footprint assessment parameters in urban drainage system, input the carbon footprint assessment parameters into Monte Carlo simulation model, and obtain dynamic prediction results of different carbon footprint assessment parameters; S3- Set pipeline network repair scenarios according to the control targets of sewage collection rate and external water intrusion rate in urban construction planning; S4- Calculate the carbon emissions of drainage pipes, sewage treatment plants and receiving water bodies in urban drainage system under baseline scenario and pipeline network repair scenario, and obtain carbon emission reduction under urban drainage system pipeline network repair scenario by comparing the carbon emissions under baseline scenario and pipeline network repair scenario.

[0011] Preferably, the water supply data collected in step S1 include household water consumption, public service water consumption and production and operation water consumption, and the data sources include local urban and rural construction statistical yearbooks and relevant data of water companies; the drainage water quality background value includes three indicators: chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP), including domestic sewage background value and industrial wastewater background value, which are used for calculation; the domestic sewage background value is determined according to the manual of domestic pollution source production and emission coefficients in the national pollution source census or on-site detection, and the industrial wastewater background value is determined according to the industrial wastewater collection concentration standard stipulated by local governments or on-site detection; the pollution generation coefficient is determined according to the manual of domestic pollution source production and emission coefficients in the national pollution source census or based on water use data of industrial enterprises; the sewage treatment plant operation data includes sewage treatment plant inlet and outlet water quality and water quantity data, sludge disposal data, resources, and energy consumption data, and the sources include local urban and rural construction statistical yearbooks and relevant data of water companies.

[0012] Preferably, in step S1, the pollution load balance of the influent of the urban sewage treatment plant is used to calculate the direct discharge of sewage and the intrusion of external water in the urban drainage system, and the calculation formula is as follows:

[0013] Q 排水,i =Q 供水,i ×f i

[0014]

[0015] Q 污水直排 =∑Q 纳管,i -∑Q 排水,i

[0016] Q 外水入侵 =∑Q 进水,i -ΣQ 纳管,i

[0017] In the above formula, i represents the type of water user (households, public buildings, industrial enterprises); fi Indicates the pollution reduction coefficient of different sewage discharge sources; Q 排水,i Indicates the discharge volume of different water users; Q 进水,i Indicates the amount of water in the sewage treatment plant; C 进水,i Indicates the pollutant influent concentration of the sewage treatment plant, which can be measured by COD, TN or TP indicators; C 本底 Indicates the drainage background value of different sewage; Q 纳管,i Indicates the actual amount of sewage entering the sewage pipe; Q 污水直排 and Q 外水入侵 It represents the direct discharge of sewage and the intrusion of external water into the urban drainage system within the accounting area.

[0018] Preferably, the collection of relevant carbon footprint assessment parameters in the urban drainage system in step S2 includes collecting carbon emission factors of relevant carbon emission activities affected by drainage network defects in the drainage pipes, sewage treatment plants and receiving water bodies in the drainage system; indirect carbon emission factors of electricity consumption in gravity flow pipes and pressure flow pipes in the drainage pipes; direct carbon emission factors of sewage biochemical treatment processes and sludge treatment and disposal processes in the sewage treatment plants, indirect carbon emission factors of additional carbon sources and flocculants added for sewage denitrification and phosphorus removal, and indirect carbon emission factors of electricity / heat energy consumed in sewage and sludge disposal; direct carbon emission factors of greenhouse gas production by biodegradation of sewage after discharge into the river in the receiving water bodies.

[0019] Preferably, the Monte Carlo simulation in step S2 is performed by Crystalball software, and the distribution type is set for different carbon emission factor data sets of the same carbon emission activity, and 100,000 simulations are performed, and the average value of the newly acquired data sets is taken to obtain the emission factor range of a certain carbon emission activity.

[0020] Preferably, the direct sewage discharge rate and external water intrusion rate in step S3 are calculated using the following formula:

[0021]

[0022] Preferably, the historical carbon emissions of the drainage pipes, sewage treatment plants and receiving water bodies in the urban drainage system in step S4 are calculated using the carbon emission factor method, and the calculated carbon emissions are the direct carbon emissions of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) produced, and the indirect carbon emissions of energy and reagent consumption, and the calculation formula is as follows:

[0023] E m,j =AD j ×EF j

[0024] In the above formula, j represents different carbon emission activities in the urban drainage system; E m,jis the greenhouse gas emissions of different carbon emission activities; AD j is the activity level data of different carbon emission activities; EF j The emission factors for different carbon emission activities can be determined by IPCC or literature recommended values.

[0025] Preferably, in the pipe network repair scenario in step S4, the water quality of the sewage treatment plant inlet water (C' 进水,i ) and water volume (Q' 进水,i ) should be adjusted according to the set pipeline repair scenario, the formula is as follows:

[0026] Q′ 进水,i =(1-sewage direct discharge rate)×Q 排水,i ×(1+external water intrusion rate)

[0027]

[0028] In the above formula, C' 进水,i and Q' 进水,i They are respectively the estimated sewage treatment plant influent water quality indicators (COD, TN and TP) and influent water volume under the pipeline network repair scenario.

[0029] Preferably, in step S4, the carbon emissions of the drainage system under the pipeline network repair scenario are recalculated and then compared with the baseline scenario to calculate the carbon emission reduction of the drainage system under the pipeline network repair scenario.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. Based on the quantitative assessment of direct sewage discharge and external water intrusion caused by drainage network defects, the present invention further quantitatively evaluates the carbon emission reduction of the urban drainage system under the drainage network repair scenario. This method can more systematically and comprehensively understand the impact of drainage network defects on carbon emissions during the operation of the urban drainage system, and clarify the scenarios with the greatest potential for carbon emission reduction after drainage network repair in the urban drainage system, providing a reference for policy makers to choose a reasonable urban carbon emission reduction path.

[0032] 2. The data processing method based on Monte Carlo simulation of the present invention can replace a single carbon emission factor parameter value with an interval parameter value, and finally perform multiple sampling fittings to obtain the distribution of output data. To a certain extent, it reduces the subjectivity of the carbon emission factor data quality in the database and references, takes into account the uncertainty of the global data, and makes the calculation results more reliable.

[0033] To summarize, the present invention takes into account the impact of drainage network repair policy orientation on the carbon emissions of urban drainage systems. It can quickly determine the impact of different network defects on carbon emissions in the drainage system's sewage / rainwater collection, transportation, treatment and discharge scenarios, thereby assisting urban drainage systems in achieving the goal of "carbon neutrality". BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 An embodiment of the present invention provides a method for calculating carbon emission reduction in an urban drainage system suitable for a pipeline repair scenario. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] like Figure 1 As shown, a carbon emission reduction accounting method for an urban drainage system in a pipeline repair scenario disclosed by the present invention includes the following steps:

[0037] S1- Collect and calculate water supply data, drainage water quality background value, pollution coefficient and operation data of sewage treatment plants in the area, calculate the direct discharge of sewage and external water intrusion of the urban drainage system to evaluate the defects of the urban drainage system network.

[0038] The water supply data collected in step S1 include household water consumption, public service water consumption and production and operation water consumption, and the data sources include local urban and rural construction statistical yearbooks and relevant data of water companies; the drainage water quality background value includes drainage pollutant background value, domestic sewage background value and industrial wastewater background value; the drainage water quality background value includes three indicators: chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP), including domestic sewage background value and industrial wastewater background value, which are used for calculation; the domestic sewage background value is determined according to the manual of domestic pollution source production and emission coefficients in the national pollution source census or on-site detection, and the industrial wastewater background value is determined according to the industrial wastewater management concentration standards or on-site detection stipulated by various localities; the pollution coefficient is determined according to the manual of domestic pollution source production and emission coefficients in the national pollution source census or based on water use data of industrial enterprises; the sewage treatment plant operation data includes sewage treatment plant inlet and outlet water quality and water quantity data, sludge disposal data, resources, and energy consumption data, and the sources include local urban and rural construction statistical yearbooks and relevant data of water companies.

[0039] In step S1, the pollution load balance of the influent of the urban sewage treatment plant is used to calculate the direct discharge of sewage and the intrusion of external water in the urban drainage system. The calculation formula is as follows:

[0040] Q 排水,i =Q 供水,i×f i

[0041]

[0042] Q 污水直排 =∑Q 纳管,i -∑Q 排水,i

[0043] Q 外水入侵 =∑Q 进水,i -∑Q 纳管,i

[0044] In the above formula, i represents the type of water user (households, public buildings, industrial enterprises); f i Indicates the pollution reduction coefficient of different sewage discharge sources; Q 排水,i Indicates the discharge volume of different water users; Q 进水,i Indicates the amount of water in the sewage treatment plant; C 进水,i Indicates the pollutant influent concentration of the sewage treatment plant, which can be measured by COD, TN or TP indicators; C 本底 Indicates the drainage background value of different sewage; Q 纳管,i Indicates the actual amount of sewage entering the sewage pipe; Q 污水直排 and Q 外水入侵 It represents the direct discharge of sewage and the intrusion of external water into the urban drainage system within the accounting area.

[0045] S2-Collect relevant carbon footprint assessment parameters in the urban drainage system, input the carbon footprint assessment parameters into the Monte Carlo simulation model, and obtain dynamic prediction results of different carbon footprint assessment parameters.

[0046] The collection of relevant carbon footprint assessment parameters in the urban drainage system in step S2 includes collecting carbon emission factors of relevant carbon emission activities in the drainage pipes, sewage treatment plants and receiving water bodies in the drainage system that are affected by drainage network defects; indirect carbon emission factors of electricity consumption in gravity flow pipes and pressure flow pipes in the drainage pipes; direct carbon emission factors of sewage biochemical treatment processes and sludge treatment and disposal processes in the sewage treatment plants, indirect carbon emission factors of additional carbon sources and flocculants added for sewage denitrification and phosphorus removal, and indirect carbon emission factors of electricity / heat energy consumed in sewage and sludge disposal; direct carbon emission factors of greenhouse gases produced by biological degradation of sewage after discharge into the river in the receiving water bodies.

[0047] The Monte Carlo simulation in step S2 is performed using Crystall ball software. The distribution type is set for different carbon emission factor data sets of the same carbon emission activity, and 100,000 simulations are performed. The average value of the newly acquired data set is taken to obtain the emission factor range of a certain carbon emission activity.

[0048] S3-Set the pipeline network repair scenario based on the control targets of sewage collection rate and external water intrusion rate in the urban construction plan.

[0049] The calculation formulas for sewage direct discharge rate and external water intrusion rate in step S3 are as follows:

[0050]

[0051]

[0052] S4-Calculate the carbon emissions of drainage pipes, sewage treatment plants and receiving water bodies in the urban drainage system under the baseline scenario and the pipeline network repair scenario. By comparing the carbon emissions under the baseline scenario and the pipeline network repair scenario, the carbon emission reduction under the urban drainage system pipeline network repair scenario is obtained.

[0053] The historical carbon emissions of the drainage pipes, sewage treatment plants and receiving water bodies in the urban drainage system described in step S4 are calculated using the carbon emission factor method. The calculated carbon emissions are the direct carbon emissions of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) produced, and the indirect carbon emissions of energy and reagent consumption. The calculation formula is as follows:

[0054] E m,j =AD j ×EF j

[0055] In the above formula, j represents different carbon emission activities in the urban drainage system; E m,j is the greenhouse gas emissions of different carbon emission activities; AD j is the activity level data of different carbon emission activities; EF j The emission factors for different carbon emission activities can be determined by IPCC or literature recommended values.

[0056] In the pipeline repair scenario in step S4, the water quality of the sewage treatment plant inlet (C' 进水,i ) and water volume (Q' 进水,i ) should be adjusted according to the set pipeline repair scenario, the formula is as follows:

[0057] Q′ 进水,i =(1-sewage direct discharge rate)×Q 排水,i ×(1+external water intrusion rate)

[0058]

[0059] In the above formula, C' 进水,i and Q' 进水,i They are respectively the estimated sewage treatment plant influent water quality indicators (COD, TN and TP) and influent water volume under the pipeline network repair scenario.

[0060] In step S4, the carbon emissions of the drainage system under the pipeline network repair scenario are recalculated and compared with the baseline scenario to calculate the carbon emission reduction of the drainage system under the pipeline network repair scenario.

[0061] The following is a detailed description with specific data.

[0062] This embodiment selects the urban drainage system of Zhejiang Province as the evaluation object, and takes 2019 as the baseline.

[0063] S1- Collect and calculate the water supply data, drainage water quality background value, pollution coefficient and operation data of sewage treatment plants in the area. The above data are shown in Table 1, Table 2 and Table 3:

[0064] Table 1. Water supply data in Zhejiang Province in 2019 (10 4 m 3 )

[0065]

[0066] Table 2. Operation data of urban sewage treatment plants in Zhejiang Province in 2019

[0067]

[0068]

[0069] Table 3. Background values ​​of drainage water quality in Zhejiang Province

[0070] Sewage Type COD(mg / L) TN(mg / L) TP(mg / L) Pollution coefficient Domestic sewage 340 44.8 4.27 0.85 Industrial wastewater <200 50 8 0.90

[0071] Using the pollution load balance of the influent of the urban sewage treatment plant, the sewage direct discharge and external water intrusion of the urban drainage system are calculated to evaluate the defects of the urban drainage system network. The calculation method is shown in formulas (1)-(4). 污水直排 2.1×10 8 m 3 , Q 外水入侵 11.0×10 8 m 3 .

[0072] S2- Input the carbon footprint assessment parameters of the urban drainage system into the Monte Carlo simulation model to obtain dynamic prediction results of different carbon footprint assessment parameters. During the operation stage of the urban drainage system, the main carbon emission activities affected by the drainage network defects in the drainage pipeline scenario are the indirect carbon emissions corresponding to the energy consumed by sewage collection and transportation (G pipe ), which is mainly estimated by the electricity consumption of sewage pumping stations and local electricity emission factors; the main carbon emission activities affected by drainage network defects in the sewage treatment plant scenario are direct carbon emissions of greenhouse gases generated by sewage biochemical treatment and sludge treatment (G plant_wastewaterand G plant_sludge ), and indirect carbon emissions from chemicals and energy consumed in sewage treatment and sludge disposal (G plant_chemical and G plant_electricity ), the former is mainly estimated by the pollution degradation load and sludge production in sewage treatment and the corresponding carbon emission factor, and the latter is mainly calculated by the amount of reagents, energy consumption and the corresponding carbon emission factor; the main carbon emission activities affected by the defects of the drainage network in the receiving water scene are the greenhouse gas emissions (G receivingwater ), which is mainly estimated through the pollution load of direct sewage discharge, the pollution load of sewage treatment plant effluent and the carbon emission factor in the receiving water body.

[0073] Furthermore, the relevant carbon emission factors are input into the Crystal ball model for Monte Carlo simulation to obtain dynamic prediction results of different carbon emission factors.

[0074] S3-Set the pipeline network repair scenario according to the control targets of sewage collection rate and external water intrusion rate in the urban construction plan;

[0075] Specifically, in this embodiment, the pipe network repair scenario is set based on a 70% sewage collection rate and a 15% external water intrusion rate.

[0076] S4-Calculate the carbon emissions of drainage pipes, sewage treatment plants and receiving water bodies in the urban drainage system under the baseline scenario and the pipeline network repair scenario, and obtain the carbon emission reduction under the urban drainage system pipeline network repair scenario through comparison.

[0077] Furthermore, the calculation formula for the total carbon emissions (G) in the above drainage system affected by the drainage network defects is as follows:

[0078] G system =G pipe +∑G plant_i +G receiving water

[0079] Specifically, the indirect carbon emissions from the drainage network G pipe The calculation formula is as follows:

[0080] G pipe =EF ele ×(Q 进水 ×75%×E gravity +Q 进水 ×25%×E electricity )

[0081] In the above formula, E gravity and E electricity The power consumption per ton of water for gravity flow pipeline and pressure flow pipeline under different scenarios (kWh / m3 ), and their water transport volume accounts for 75% and 25% of the total sewage volume respectively. ele is the local electricity emission factor. The results show that in 2019, the urban drainage system in Zhejiang Province under the baseline scenario and pipeline repair scenario G pipe They are (15.9±1.7)×10 4 tCO2e and (10.4±0.8)×10 4 tCO2e.

[0082] Specifically, the calculation formula for direct carbon emissions and indirect carbon emissions in sewage treatment plants is as follows: G plant_wastewater =Q 进水 ×∑C 进水 ,i×EF wastewater,i

[0083] G plant_sludge =DM sludge ×EF sludge

[0084] G plant_chemical =∑M i ×EF i,chemical

[0085] G plant_electricity =∑E i ×EF ele

[0086] In the above formula, Q 进水 and C 进水 are the influent volume and water quality (COD or TN) of the sewage treatment plant under different scenarios, EF wastewater,i is the emission factor of CO2, CH4 or N2O in the process of biological treatment of sewage (kgCO2e / kgCOD or kgCO2e / kgTN); DM sludge is the dry sludge output of the sewage treatment plant under different scenarios, EF sludge is the CO2 or N2O emission factor of dry sludge disposal under different scenarios (kgCO2e / kgDM); M i is the amount of chemicals used in each process of the sewage treatment plant under different scenarios, EF i,chemcial is the carbon emission factor of different agents (kgCO2e / kgChemical); E i is the power consumption of each process link of the sewage treatment plant under different scenarios. The results show that ∑G plant,i They are (220.8±6.8)×10 4 tCO2e and (215.3±5.4)×10 4 tCO2e.

[0087] Specifically, the calculation formula for direct carbon emissions in receiving water bodies is as follows:

[0088] G receiving water =∑(Q 污水直排 ×C 本底 +Q 出水 ×C 出水 )×EF water,i

[0089] In the above formula, EF water,i is the carbon emission factor of CH4 or N2O in natural water (kgCO2e / kg COD or kgCO2e / kgTN). The results show that in 2019, under the baseline scenario and pipeline repair scenario of urban drainage system in Zhejiang Province, G receivingwater They are (79.1±6.8)×10 4 tCO2e and (26.1±5.4)×10 4 tCO2e.

[0090] In summary, compared with the baseline situation, the urban drainage system can achieve 64×10 4 Annual emission reduction of tCO2e.

[0091] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0092] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for calculating carbon emission reduction in urban drainage systems in pipeline repair scenarios, characterized in that: The steps include: S1- Collect and calculate water supply data, drainage water quality background value, pollution coefficient and operation data of sewage treatment plants in the area, calculate the direct discharge of sewage and external water intrusion of urban drainage system to evaluate the defects of urban drainage system network; S2-collect relevant carbon footprint assessment parameters in the urban drainage system, input the carbon footprint assessment parameters into the Monte Carlo simulation model, and obtain dynamic prediction results of different carbon footprint assessment parameters; S3-Set the pipeline network repair scenario according to the control targets of sewage collection rate and external water intrusion rate in the urban construction plan; S4-Calculate the carbon emissions of drainage pipes, sewage treatment plants and receiving water bodies in the urban drainage system under the baseline scenario and the pipeline network repair scenario. By comparing the carbon emissions under the baseline scenario and the pipeline network repair scenario, the carbon emission reduction under the urban drainage system pipeline network repair scenario is obtained.

2. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: The water supply data collected in step S1 include household water consumption, public service water consumption and production and operation water consumption, and the data sources include local urban and rural construction statistical yearbooks and relevant data of water companies; the drainage water quality background value includes three indicators: chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP), including domestic sewage background value and industrial wastewater background value, which are used for calculation; the domestic sewage background value is determined according to the manual of domestic pollution source production and emission coefficients in the national pollution source census or on-site detection, and the industrial wastewater background value is determined according to the industrial wastewater management concentration standards or on-site detection stipulated by local governments; the pollution generation coefficient is determined according to the manual of domestic pollution source production and emission coefficients in the national pollution source census or based on water use data of industrial enterprises; the sewage treatment plant operation data includes sewage treatment plant inlet and outlet water quality and water quantity data, sludge disposal data, resources, and energy consumption data, and the sources include local urban and rural construction statistical yearbooks and relevant data of water companies.

3. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: In step S1, the pollution load balance of the influent of the urban sewage treatment plant is used to calculate the direct discharge of sewage and the intrusion of external water in the urban drainage system. The calculation formula is as follows: Q 排水i =Q 供水，i ×f i Q 污水直排 =Σ Q 纳管，i -SQ 排水，i Q 外水入侵 =∑Q 进水，i -ΣQ 纳管，i In the above formula, i represents the type of water user (households, public buildings, industrial enterprises); fi represents the pollution reduction coefficient of different sewage discharge sources; Q 排水,i Indicates the discharge volume of different water users; Q 进水 , i represents the water volume of the sewage treatment plant; C 进水 , i represents the pollutant influent concentration of the sewage treatment plant, which can be measured by COD, TN or TP; C 本底 Indicates the drainage background value of different sewage; Q 纳管 , i represents the actual amount of sewage entering the sewage pipe; Q 污水直排 and Q 外水入侵 It represents the direct discharge of sewage and the intrusion of external water into the urban drainage system within the accounting area.

4. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: Collecting relevant carbon footprint assessment parameters in the urban drainage system in step S2 includes collecting carbon emission factors of relevant carbon emission activities in the drainage pipes, sewage treatment plants and receiving water bodies in the drainage system that are affected by the defects of the drainage network; The indirect carbon emission factor of electricity consumption in the drainage pipeline, specifically in the gravity flow pipeline and the pressure flow pipeline; Specifically, the direct carbon emission factors of the sewage biochemical treatment process and the sludge treatment and disposal process in the sewage treatment plant, the indirect carbon emission factors of the additional carbon source and flocculant added for sewage denitrification and phosphorus removal, and the indirect carbon emission factors of the electricity / heat energy consumed in sewage and sludge disposal; The receiving water body specifically refers to the direct carbon emission factor for greenhouse gases produced by biodegradation of sewage after it is discharged into the river.

5. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: The Monte Carlo simulation in step S2 is performed using Crystallball software. The distribution type is set for different carbon emission factor data sets of the same carbon emission activity, and 100,000 simulations are performed. The average value of the newly acquired data set is taken to obtain the emission factor range of a certain carbon emission activity.

6. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: The calculation formulas for sewage direct discharge rate and external water intrusion rate in step S3 are as follows:

7. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: The historical carbon emissions of the drainage pipes, sewage treatment plants and receiving water bodies in the urban drainage system described in step S4 are calculated using the carbon emission factor method. The calculated carbon emissions are the direct carbon emissions of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) produced, and the indirect carbon emissions of energy and reagent consumption. The calculation formula is as follows: AND m，j =AD j ×EF j In the above formula, j represents different carbon emission activities in the urban drainage system; E m,j is the greenhouse gas emissions of different carbon emission activities; AD j is the activity level data of different carbon emission activities; EF j The emission factors for different carbon emission activities can be determined by IPCC or literature recommended values.

8. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: In the pipeline repair scenario in step S4, the water quality of the sewage treatment plant inlet (C' 进水,i ) and water volume (Q' 进水,i ) should be adjusted according to the set pipeline repair scenario, the formula is as follows: Q′ 进水，i =(1-sewage direct discharge rate)×Q 排水，i ×(1+external water intrusion rate) In the above formula, C' 进水,i and Q' 进水,i They are respectively the estimated sewage treatment plant influent water quality indicators (COD, TN and TP) and influent water volume under the pipeline network repair scenario.

9. According to the method for calculating carbon emission reduction of urban drainage system in pipeline repair scenario described in claim 1, it is characterized by: In step S4, the carbon emissions of the drainage system under the pipeline network repair scenario are recalculated and compared with the baseline scenario to calculate the carbon emission reduction of the drainage system under the pipeline network repair scenario.

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