Urban water pollutant balance measuring and calculating method and system

Abstract

The invention discloses an urban water pollutant balance measurement and calculation method and system, and the method comprises the steps: firstly constructing a target urban water pollutant basic database, carrying out the overall balance measurement and calculation of regional water pollutants based on the water pollutant basic database, and obtaining the overall balance measurement and calculation result of the regional water pollutants. Then, an in-situ control experiment is conducted on the drainage system, a pipeline-river channel multi-element monitoring system is built for monitoring, then a pipe network-discharge port-river channel integrated numerical model is built, and space-time distribution is conducted on water pollutants in the balance process of generation, discharge and river entering; according to the method, the function of accurately measuring and calculating the balance of the water pollutants of the urban drainage system by integrating a triangular diagram method, an in-situ observation method and a numerical model method is realized, so that model debugging distortion caused by a pipe network structure error is avoided, and the dynamic evolution process of the water pollutants can be better reflected; the method has important significance in guiding accurate prevention and control of urban water pollution and targeted treatment of water environment, and is suitable for being widely popularized and used.

Description

Technical Field

[0001] The present invention relates to the technical field of calculating the balance of water pollutants, and particularly to a method and system for calculating the balance of urban water pollutants. Background Art

[0002] Urban drainage systems are essential lifeline projects in modern cities. An efficient, complete, and sustainable drainage system is of decisive significance for ensuring urban safety, improving the living environment, protecting the ecological environment, and the sustainable utilization of water resources. Facing the dual pressures of climate change and urbanization, building a "green, resilient, and intelligent" modern drainage system is the future development direction. Urban drainage systems usually have various different modes and their combined forms, such as separate systems, combined systems, and direct discharge systems.

[0003] Currently, due to the complexity of urban drainage systems and most of them being in underground spaces, and at the same time, the misconnections, leaks, mixed connections, and seepage in the pipe networks are concealed and uncertain, it leads to the coexistence of the overflow of combined sewer pipes into rivers and the backflow of river water into combined sewer pipes through overflow outlets in urban drainage systems. This not only makes it difficult to accurately quantify the amount of water pollutants entering the river in urban drainage systems but also severely restricts the precise tracing of pollution in urban complex water systems under the background of rapid urbanization. This has become the key crux for improving the urban water environment; therefore, it is necessary to design a method and system for calculating the balance of urban water pollutants. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art. To better and effectively solve the problems that existing urban drainage systems are complex and mostly in underground spaces, and at the same time, the misconnections, leaks, mixed connections, and seepage in the pipe networks are concealed and uncertain, resulting in the coexistence of the overflow of combined sewer pipes into rivers and the backflow of river water into combined sewer pipes through overflow outlets in urban drainage systems, which not only makes it difficult to accurately quantify the amount of water pollutants entering the river in urban drainage systems but also severely restricts the precise tracing of pollution in urban complex water systems under the background of rapid urbanization. The present invention provides a method and system for calculating the balance of urban water pollutants, which realizes the function of accurately calculating the balance of water pollutants in urban drainage systems by integrating the triangular graph method, in-situ observation method, and numerical model method, and can timely correct the pipe network topological structure and calibrate and verify the hydrodynamic numerical simulation of the pipe network-river. This not only avoids the distortion of model debugging caused by incorrect pipe network structures but also can better reflect the dynamic evolution process of water pollutants, which is of great significance for guiding the precise prevention and control of urban water pollution and the targeted treatment of the water environment.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for calculating the balance of urban water pollutants, comprising the following steps, Step A, constructing a basic database of water pollutants in the target city; Step B: Based on the water pollutant basic database, use the pollution reduction coefficient method and the proportional coefficient method to calculate the sewage generation volume of each industry and the direct sewage discharge volume of the plot respectively, and use the chemical mass and water volume balance equation to measure the equivalent sewage treatment volume. Then, use the triangle graphical method to divide the flow curve to measure the external water inflow into the pipe network, so as to conduct an overall balance measurement of regional water pollutants and obtain the overall balance measurement result of regional water pollutants; Step C: Conduct in-situ control experiments on the drainage system and establish a multi-element monitoring system for pipelines and rivers for monitoring to obtain monitoring data. Then, quantitatively analyze the response relationship between the river water level and the pipeline network liquid level changes based on the monitoring data and correct the topological relationship between the pipeline network and the river; Step D: Use the corrected topological relationship between the pipeline network and the river to construct an integrated numerical model of the pipeline network - drainage outlet - river for the drainage system. Then, use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of the pipeline network - drainage outlet - river and obtain the verified integrated numerical model of the pipeline network - drainage outlet - river; Step E: Use the overall balance measurement result of regional water pollutants and the verified integrated numerical model of the pipeline network - drainage outlet - river to conduct spatio-temporal quantitative measurement of the urban water production and drainage pollutant balance volume and obtain the quantitative measurement result of the urban water pollutant balance, thus completing the urban water pollutant balance measurement operation.

[0006] The above-mentioned method for measuring the urban water pollutant balance, step A: Construct a basic database of water pollutants for the target city. The water pollutant basic database includes static data and dynamic data. The static data includes the target city's population scale data, land use area data, pipeline network vector data, river vector data, drainage outlet data, and pumping station data. The dynamic data includes the urban residential tap water sales volume, industrial and service industry water sales volume, special industry water sales volume, daily rainfall, sewage online monitoring data of enterprises with online monitoring, water use and drainage data of enterprises without online monitoring, urban sewage treatment plant sewage treatment volume, and the influent COD concentration of the sewage treatment plant. Among them, the urban residential tap water sales volume includes residential domestic water sales volume, non-residential domestic water sales volume, secondary water supply sales volume, and special hardship preferential water sales volume; The specific construction process of the water pollutant basic database is formed by decomposing the dynamic data according to the water supply areas of waterworks and the drainage areas of sewage treatment plants and combining the population scale data and land use area data of each administrative unit in the target city.

[0007] The aforementioned method for calculating the balance of urban water pollutants, step B: Based on the basic database of water pollutants, the sewage generation volume of each industry and the direct sewage discharge volume of plots are calculated respectively by using the pollution coefficient method and the proportional coefficient method, and the equivalent sewage treatment volume is calculated by using the chemical mass and water volume balance equation. Then, the triangular diagram method is used to divide the flow curve to calculate the amount of external water flowing into the pipe network, so as to conduct an overall balance calculation of regional water pollutants and obtain the overall balance calculation result of regional water pollutants. The overall balance calculation result of regional water pollutants includes sewage generation volume, sewage treatment volume, direct sewage discharge volume and the amount of external water flowing into the pipe network. The specific steps are as follows: Step B1: Calculate the sewage generation volume of each industry by using the pollution coefficient method, where the sewage generation volume is equal to the product of the water consumption and the corresponding pollution coefficient. Among them, the pollution coefficient of urban domestic water is taken as 0.8 - 0.9, the pollution coefficient of industrial water is taken as 0.78, and the pollution coefficients of service industries and special industries are taken as 0.82 and 0.9 respectively. Step B2: Calculate the direct sewage discharge volume of each industry plot by using the proportional coefficient method, where the direct sewage discharge volume of the plot is specifically calculated by using the plot product quantity and the direct discharge coefficient estimated according to the pipe network. Among them, for communities without laid pipe networks, the direct discharge rate is taken as 100%, and for communities with laid pipe networks but with mixed connections of balcony risers and direct discharge rates of mixed connections in the first - floor garages taken as 4%. Step B3: Calculate the equivalent sewage treatment volume by using the chemical mass and water volume balance equation. Specifically, the equivalent sewage treatment volume of the urban sewage treatment plant is calculated by using the chemical mass and water volume balance relationship of the water quality characteristic factors of the drainage system. The calculation process of using chemical oxygen demand (COD) to replace water volume as the measurement factor and using the chemical mass and water volume balance equation for calculation is shown in formula (1). , (1) Among them, is the total flow of sewage into the sewage treatment plant under dry - weather conditions, is the amount of raw sewage, is the inflow and infiltration volume of external water including groundwater and surface water, , and are the concentrations of water quality characteristic factors of total sewage, raw sewage and external water respectively under dry - weather conditions; Step B4: Use the triangular diagram method to divide the flow curve to calculate the amount of external water flowing into the pipe network. Specifically, according to the chemical mass and water volume balance equation, the flow curve at the outlet of the sewage pipe network within the corresponding time period is divided, and then the daily flow values within the selected time period at the end of the sewage pipe network are arranged in ascending order to form an S - shaped curve.

[0008] Among them, the percentage P of the amount of external water flowing into the pipe network in the influent volume of the sewage treatment plant can divide the evaluation level of the external water problem into four levels, including general (P < 15%), relatively serious (15% < P < 35%), serious (35% <= P < 55%), and extremely serious (P >= 55%); The above-mentioned method for calculating the balance of urban water pollutants, step C, conducts in-situ control experiments on the drainage system and establishes a multi-element monitoring system for pipelines and rivers for monitoring, so as to obtain monitoring data, and then quantitatively analyzes the response relationship between the changes of the river water level and the pipe network liquid level according to the monitoring data and corrects the topological relationship between the pipe network and the river. The specific steps are as follows: Step C1, conduct in-situ control experiments on the drainage system. Specifically, the control variable method is used to regulate the river water level and the pipe network liquid level respectively. The specific steps are as follows: Step C11, control of the river water level. Specifically, first turn on the river drainage pump station and lower the river water level, then adjust the pumping flow of the pump station and maintain the river water level, then turn off the pump station and monitor the slow process of the water level rising, then open the water replenishment gate and monitor the obvious process of the river water level rising, and then increase the opening of the gate and monitor the accelerated process of the water level rising; Step C12, control of the pipeline sewage lift pump station. Specifically, first turn off one sewage lift pump station, then turn off another sewage lift pump station, then turn off one sewage lift pump station, and then turn off all integrated pump stations. At the same time, monitor the change process of the pipeline liquid level; Step C13, airbag plugging control. Specifically, block the sewage intercepting pipes on both sides of the river with airbags and clarify the plugging points for plugging according to the actual situation, then divide the pipeline into two independent pipelines and monitor the changes of the pipeline liquid levels of the two pipelines under the superposition of the river water level control respectively; Step C14, pipeline branch control. Specifically, block the connected pipelines with airbags, then control the different diversion ports of the pipe sections and monitor the changes of the liquid levels of different pipe sections separately; Step C2, establish a multi-element monitoring system for pipelines and rivers for monitoring. Among them, the multi-element monitoring system for pipelines and rivers specifically monitors the pipeline liquid level, river water level, diversion port flow rate and video during the in-situ control experiment of the drainage system. The specific steps are as follows: Step C21, monitoring of the pipeline liquid level and the river water level. Specifically, use pipeline liquid level gauges to monitor each target pipeline, and then use river float water level gauges to monitor the upstream and downstream of each target river, and synchronously monitor the river water level near the sewage well; Step C22, monitoring of the pipeline intersection flow rate. Specifically, install fixed flow meters on site when the pipe network bifurcates; Step C23, pipeline video monitoring. Use a closed-circuit television monitoring system to detect pipeline seepage anomalies endoscopically.

[0009] The aforementioned method for calculating the urban water pollutant balance, step D: Construct an integrated numerical model of the drainage system network - outfall - river using the modified topological relationship between the network and the river, and then calibrate and verify the model parameters of the integrated numerical model of the network - outfall - river using the monitoring data to obtain the verified integrated numerical model of the network - outfall - river. The specific steps are as follows: Step D1: Construct an integrated numerical model of the drainage system network - outfall - river using the modified topological relationship between the network and the river, where the integrated numerical model of the network - outfall - river includes a rainfall - runoff module, a pipe - flow calculation module, a water - quality module, and a real - time control module; Step D2: Calibrate and verify the model parameters of the integrated numerical model of the network - outfall - river using the monitoring data to obtain the verified integrated numerical model of the network - outfall - river. The calibration and verification indicators use the Nash - Sutcliffe efficiency coefficient NSE, the percent bias PBIAS, and the ratio coefficient RSR of the root - mean - square error to the standard deviation of the observations. The Nash - Sutcliffe efficiency coefficient NSE is used to quantify the calculation accuracy of the integrated numerical model of the network - outfall - river by the relative magnitude of the residual variance and the variance of the measured data. The percent bias PBIAS is used to measure the average trend of the data deviating from the observed data. The ratio coefficient RSR of the root - mean - square error to the standard deviation of the observations is used to standardize the root - mean - square error by the standard deviation of the observed values.

[0010] Among them, the value range of the Nash - Sutcliffe efficiency coefficient NSE is (-∞, 1]. The closer it is to 1, the better the model prediction ability. The closer the percent bias PBIAS is to 0, the more accurate the calculation effect. A positive value indicates that the model has an underestimation bias, and vice versa, there is an overestimation bias. The closer the ratio coefficient RSR of the root - mean - square error to the standard deviation of the observations is to 0, the better the model simulation performance. If the Nash - Sutcliffe efficiency coefficient NSE > 0.5, the ratio coefficient RSR of the root - mean - square error to the standard deviation of the observations < 0.7, and the percent bias PBIAS of the runoff and pollutant calculations are respectively and respectively, then it indicates that the calculation effect is relatively reliable; The aforementioned method for calculating the urban water pollutant balance, the specific steps of step D1 are as follows: Step D11: Construct a rainfall - runoff module, where the rainfall - runoff module uses the Horton infiltration formula, as shown in formula (2): (2) Among them, is the infiltration rate, is the steady infiltration rate, is the initial infiltration rate, is the rainfall time, is the decay constant; Step D12, construct a pipe flow calculation module, where the pipe flow calculation module adopts the Saint-Venant equations of unsteady open-channel flow partial differential equations. The specific steps are as follows: Step D121, establish the mass conservation equation and the momentum conservation equation, as shown in formula (3): , (3); where is the flow rate, is the cross-sectional area, is the acceleration due to gravity, is the horizontal angle, is the bed slope, is the conveyance; Step D122, use the Manning formula to measure the steady flow of the river, as shown in formula (4): (4) where is the roughness coefficient, is the hydraulic radius, is the bottom slope of the river channel; Step D13, construct a water quality module, where the water quality module uses a one-dimensional advection-diffusion model to calculate the advection-diffusion process of soluble and suspended substances in water, as shown in formula (5): , (5) where is the concentration of the substance, is the diffusion time, is the average flow velocity of the river, is the spatial coordinate, is the advection-diffusion coefficient, is the first-order decay coefficient of the substance, and are the empirical parameters of the advection-diffusion coefficient; Step D14, construct a real-time control module, where the real-time control module is used to control the gate and pump station scheduling operations in the drainage system and change the scheduling rules by setting measurement parameters to achieve water flow measurement.

[0011] For the aforementioned urban water pollutant balance measurement method, the specific calibration and verification process in step D2 is as shown in formula (6): , , ;(6) where is the number of simulation data, is the th measured value, is the average value of the measured values, is the th simulated value, is the average value of the simulated values.

[0012] For the above-mentioned method for calculating the balance of urban water pollutants, step E: Use the overall balance calculation result of regional water pollutants and the verified integrated numerical model of pipe network - outfall - river to conduct spatio-temporal quantitative calculation of the balance of urban production and drainage pollutants and obtain the quantitative calculation result of urban water pollutant balance, thereby completing the operation of calculating the balance of urban water pollutants. Specifically, make a time series of the obtained overall balance calculation result of regional water pollutants on a daily scale and use it as the input variable of the verified integrated numerical model of pipe network - outfall - river. Then, use the verified integrated numerical model of pipe network - outfall - river to reproduce and decompose the spatio-temporal process of calculating the balance of urban production - drainage pollutants as a whole and obtain the spatio-temporal quantitative calculation results of the pollutant production and discharge processes under the urban water use - drainage process, thereby obtaining the quantitative calculation result of urban water pollutant balance.

[0013] An urban water pollutant balance calculation system includes a database construction module, an overall balance calculation module, a multi-factor monitoring module, a numerical model establishment module, and a spatio-temporal quantitative calculation module. The database construction module is used to construct a basic database of urban water pollutants for the target city; The overall balance calculation module is used to calculate the sewage production of each industry and the direct sewage discharge of plots respectively by using the pollution coefficient method and the proportional coefficient method based on the basic database of water pollutants, and use the chemical mass and water balance equation to calculate the equivalent sewage treatment volume. Then, use the triangular graph method to divide the flow curve to calculate the amount of external water flowing into the pipe network, so as to conduct an overall balance calculation of regional water pollutants and obtain the overall balance calculation result of regional water pollutants; The multi-factor monitoring module is used to conduct in-situ control experiments on the drainage system and establish a multi-factor monitoring system for pipes - rivers for monitoring, so as to obtain monitoring data. Then, quantitatively analyze the response relationship between the changes in river water levels and pipe network liquid levels based on the monitoring data and correct the topological relationship between the pipe network and the river; The numerical model establishment module is used to construct an integrated numerical model of pipe network - outfall - river for the drainage system by using the corrected topological relationship between the pipe network and the river. Then, use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of pipe network - outfall - river and obtain the verified integrated numerical model of pipe network - outfall - river; The spatio-temporal quantitative calculation module is used to perform spatio-temporal quantitative calculation on the urban production and drainage pollutant balance quantity by using the overall balance calculation result of regional water pollutants and the verified integrated numerical model of pipe network-outfall-river, and obtain the urban water pollutant balance quantitative calculation result, so as to complete the urban water pollutant balance calculation operation.

[0014] The beneficial effects of the present invention are as follows: For a method and system for calculating the urban water pollutant balance of the present invention, first, a basic database of urban water pollutants is constructed. Then, based on the basic database of water pollutants, the sewage generation amounts of various industries and the direct sewage discharge amounts of plots are calculated respectively by using the pollution coefficient method and the proportional coefficient method, and the equivalent sewage treatment amount is calculated by using the chemical mass and water volume balance equations. Next, the triangle diagram method is used to divide the flow curve to calculate the amount of external water flowing into the pipe network, so as to perform an overall balance calculation on regional water pollutants and obtain the overall balance calculation result of regional water pollutants. Subsequently, in-situ control experiments are carried out on the drainage system and a multi-element monitoring system of pipes and rivers is established for monitoring, so as to obtain monitoring data. Then, the response relationship between the changes of river water levels and pipe network liquid levels is quantitatively analyzed according to the monitoring data and the topological relationship between the pipe network and the river is corrected. Then, an integrated numerical model of pipe network-outfall-river of the drainage system is constructed by using the corrected topological relationship between the pipe network and the river. Then, the model parameters of the integrated numerical model of pipe network-outfall-river are calibrated and verified by using the monitoring data, and the verified integrated numerical model of pipe network-outfall-river is obtained. Finally, the spatio-temporal quantitative calculation of the urban production and drainage pollutant balance quantity is carried out by using the overall balance calculation result of regional water pollutants and the verified integrated numerical model of pipe network-outfall-river, and the urban water pollutant balance quantitative calculation result is obtained, so as to complete the urban water pollutant balance calculation operation; effectively realize the function of the water pollutant balance calculation method and system to accurately calculate the urban drainage system water pollutant balance by integrating the triangle diagram method, the in-situ observation method and the numerical model method, and through in-situ control experiments on the drainage system and a multi-element monitoring system of pipes and rivers, the pipe network topological structure can be corrected in time and the pipe network-river hydrodynamic numerical calculation can be calibrated and verified, which not only avoids the distortion of model debugging caused by incorrect pipe network structure, but also can better reflect the dynamic evolution process of water pollutants, provides a new method for accurately quantitatively calculating the spatio-temporal changes of urban water pollution load under changing scenarios, and has important significance for guiding the accurate prevention and control of urban water pollution and the targeted treatment of water environment, makes up for the defect of insufficient accuracy of traditional methods in spatio-temporal dynamic calculation of urban water pollutants under the background of rapid urbanization, and significantly improves the reliability of pollution source tracing under complex urban water systems. Brief Description of the Drawings

[0015] Figure 1 is the overall flow chart of a method for calculating the urban water pollutant balance of the present invention; Figure 2It is a schematic diagram of the urban water collection sub-region and the pipe network - outfall - river system of the present invention. Specific embodiments

[0016] The present invention will be further described below in conjunction with the accompanying drawings of the specification.

[0017] As Figure 1 shown, a method for calculating the balance of urban water pollutants of the present invention includes the following steps. Step A, constructing a basic database of urban water pollutants. The basic database of water pollutants includes static data and dynamic data. The static data includes the target urban population scale data, land use area data, pipe network vector data, river vector data, outfall data, and pumping station data. The dynamic data includes the urban residential tap water sales volume, industrial and service water sales volume, special industry water sales volume, daily rainfall, sewage online monitoring data of enterprises with online monitoring, water intake and drainage data of enterprises without online monitoring, urban sewage treatment plant sewage treatment volume, and the influent COD concentration of the sewage treatment plant. Among them, the urban residential tap water sales volume includes residential living water sales volume, non-residential living water sales volume, secondary water supply sales volume, and special hardship preferential water sales volume. The specific construction process of the basic database of water pollutants is formed by decomposing the dynamic data according to the water supply sub-regions of waterworks and the sewage drainage sub-regions of sewage treatment plants, and combining the target urban administrative unit population scale data and land use area data.

[0018] Step B, based on the basic database of water pollutants, using the sewage pollution coefficient method and the proportional coefficient method to calculate the sewage generation volume of each industry and the direct sewage discharge volume of plots respectively, and using the chemical mass and water volume balance equation to calculate the equivalent sewage treatment volume. Then, using the triangular graph method to divide the flow curve to calculate the amount of external water flowing into the pipe network, so as to conduct an overall balance calculation of regional water pollutants and obtain the overall balance calculation result of regional water pollutants. The overall balance calculation result of regional water pollutants includes sewage generation volume, sewage treatment volume, direct sewage discharge volume, and the amount of external water flowing into the pipe network. The specific steps are as follows. Step B1, using the sewage pollution coefficient method to calculate the sewage generation volume of each industry, where the sewage generation volume is equal to the product of the water consumption and the corresponding sewage pollution coefficient. Step B2, using the proportional coefficient method to calculate the direct sewage discharge volume of each industry plot, where the direct sewage discharge volume of the plot is specifically calculated by using the plot product quantity and the direct discharge coefficient estimated according to the pipe network. Step B3, using the chemical mass and water volume balance equation to calculate the equivalent sewage treatment volume. Specifically, the equivalent sewage treatment volume of the urban sewage treatment plant is calculated by using the chemical mass and water volume balance relationship of the water quality characteristic factors of the drainage system. The calculation process of using chemical oxygen demand (COD) to replace water volume as the measurement factor and using the chemical mass and water volume balance equation for calculation is shown in formula (1). , (1) Among them, is the total influent flow of sewage treatment plant under dry weather conditions, is the raw sewage volume, is the infiltration and inflow of external water including groundwater and surface water, , and are the concentration of water quality characteristic factors of total sewage, raw sewage and external water under dry weather conditions respectively; Step B4, use the triangular graph method to divide the flow curve to measure the inflow of external water into the pipe network. Specifically, divide the flow curve at the outlet of the sewage pipe network during the corresponding time period according to the chemical mass and water volume balance equation, and then arrange the daily flow values within the selected time period at the end of the sewage pipe network in ascending order to form an S-shaped curve.

[0019] Step C, conduct in-situ control experiments on the drainage system and establish a multi-element monitoring system for pipelines and rivers for monitoring, so as to obtain monitoring data, and then quantitatively analyze the response relationship between the river water level and the pipeline liquid level changes and correct the topological relationship between the pipeline and the river according to the monitoring data. The specific steps are as follows. Step C1, conduct in-situ control experiments on the drainage system. Specifically, use the method of controlling variables to regulate the river water level and the pipeline liquid level respectively. The specific steps are as follows. Step C11, control of the river water level. Specifically, first start the river pumping station and lower the river water level, then adjust the pumping flow of the pumping station and maintain the river water level, then close the pumping station and monitor the slow process of water level rise, then open the water replenishment gate and monitor the obvious process of river water level rise, and then increase the opening of the gate and monitor the accelerated process of water level rise; Step C12, control of the pipeline sewage lift pump station. Specifically, first close one sewage lift pump station, then close another sewage lift pump station, then close one sewage lift pump station, and then close all integrated pump stations. At the same time, monitor the change process of the pipeline liquid level; Step C13, airbag plugging control. Specifically, block the sewage interception pipes on both sides of the river with airbags and clarify the plugging points for plugging according to the actual situation, and then divide the pipeline into two independent pipelines and monitor the changes of the pipeline liquid levels in the two pipelines under the superposition of river water level control; Step C14, pipeline branch control. Specifically, block the connected pipelines with airbags, and then control the different diversion ports of the pipeline sections and monitor the liquid level changes of different pipeline sections separately; Step C2, establish a pipeline-river multi-element monitoring system for monitoring. The pipeline-river multi-element monitoring system specifically monitors the pipeline liquid level, river water level, flow rate at the diversion point, and video during the in-situ control experiment of the drainage system. The specific steps are as follows: Step C21, monitor the pipeline liquid level and river water level. Specifically, use a pipeline liquid level gauge to monitor each target pipeline, and then use a river float water level gauge to monitor the upstream and downstream of each target river, and synchronously monitor the river water level near the sewage well. Step C22, monitor the flow rate at the pipeline intersection. Specifically, install a fixed flow meter on-site when encountering a pipeline network bifurcation. Step C23, monitor the pipeline video. Use a closed-circuit television monitoring system to detect pipeline seepage anomalies endoscopically.

[0020] As Figure 2 shown, in step D, construct an integrated numerical model of the drainage system pipeline network-outfall-river using the corrected topological relationship between the pipeline network and the river. Then, use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of the pipeline network-outfall-river and obtain the verified integrated numerical model of the pipeline network-outfall-river, and the specific steps are as follows: Step D1, construct an integrated numerical model of the drainage system pipeline network-outfall-river using the corrected topological relationship between the pipeline network and the river. The integrated numerical model of the pipeline network-outfall-river includes a rainfall runoff module, a pipe flow calculation module, a water quality module, and a real-time control module. Step D2, use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of the pipeline network-outfall-river and obtain the verified integrated numerical model of the pipeline network-outfall-river. The calibration and verification indicators use the Nash efficiency coefficient NSE, the percentage bias PBIAS, and the ratio coefficient RSR of the root mean square error to the standard deviation of the observations. The Nash efficiency coefficient NSE is used to quantify the calculation accuracy of the integrated numerical model of the pipeline network-outfall-river using the relative size of the residual variance and the variance of the measured data. The percentage bias PBIAS is used to measure the average trend of the data deviating from the observed data. The ratio coefficient RSR of the root mean square error to the standard deviation of the observations is used to standardize the root mean square error using the standard deviation of the observed values.

[0021] The specific steps of step D1 are as follows: Step D11, construct a rainfall runoff module. The rainfall runoff module uses the Horton infiltration formula, as shown in formula (2). (2) where is the infiltration rate, is the stable infiltration rate, is the initial infiltration rate, is the rainfall time, is the attenuation constant; Step D12: Construct a pipe flow calculation module, where the pipe flow calculation module uses the Saint-Venant equations of unsteady open-channel flow partial differential equations. The specific steps are as follows: Step D121: Establish the mass conservation equation and the momentum conservation equation, as shown in formula (3): , (3); where, is the flow rate, is the cross-sectional area, is the acceleration due to gravity, is the horizontal angle, is the bed slope, is the conveyance; Step D122: Use the Manning formula to measure the steady flow of the river, as shown in formula (4): (4) where, is the roughness coefficient, is the hydraulic radius, is the bottom slope of the river channel; Step D13: Construct a water quality module, where the water quality module uses a one-dimensional advection-diffusion model to calculate the advection-diffusion process of soluble and suspended substances in water, as shown in formula (5): , (5) where, is the concentration of the substance, is the diffusion time, is the average flow velocity of the river, is the spatial coordinate, is the advection-diffusion coefficient, is the first-order attenuation coefficient of the substance, and are the empirical parameters of the advection-diffusion coefficient; Step D14: Construct a real-time control module, where the real-time control module is used to control the gate and pump station scheduling operations in the drainage system and change the scheduling rules by setting measured parameters to achieve water flow measurement.

[0022] The specific calibration and verification process of Step D2 is as shown in formula (6): , , ;(6) Among them, is the number of simulated data, is the th measured value, is the average value of the measured values, is the th simulated value, is the average value of the simulated values.

[0023] Step E: Using the overall balance calculation results of regional water pollutants and the verified integrated numerical model of pipe network - outfall - river channel, conduct spatio - temporal quantitative calculation of the pollutant balance quantity of urban production and drainage, and obtain the spatio - temporal quantitative calculation results of urban water pollutant balance, so as to complete the calculation operation of urban water pollutant balance. Specifically, make a time series of the obtained overall balance calculation results of regional water pollutants on a daily scale and use it as the input variable of the verified integrated numerical model of pipe network - outfall - river channel. Then, use the verified integrated numerical model of pipe network - outfall - river channel to reproduce and decompose the spatio - temporal process of the urban production - drainage pollutant balance calculation as a whole, and obtain the spatio - temporal quantitative calculation results of the pollutant production and discharge processes under the urban water use - drainage process, so as to obtain the spatio - temporal quantitative calculation results of urban water pollutant balance.

[0024] An urban water pollutant balance calculation system includes a database construction module, an overall balance calculation module, a multi - element monitoring module, a numerical model establishment module, and a spatio - temporal quantitative calculation module. The database construction module is used to construct the basic database of urban water pollutants of the target city; The overall balance calculation module is used to calculate the sewage production of each industry and the direct sewage discharge of plots respectively by using the pollution reduction coefficient method and the proportional coefficient method based on the basic database of water pollutants, and calculate the equivalent sewage treatment volume by using the chemical mass and water volume balance equations. Then, use the triangular graph method to divide the flow curve to calculate the amount of external water flowing into the pipe network, so as to conduct an overall balance calculation of regional water pollutants and obtain the overall balance calculation results of regional water pollutants; The multi - element monitoring module is used to conduct in - situ control experiments on the drainage system and establish a multi - element monitoring system for pipes - rivers to conduct monitoring, so as to obtain monitoring data. Then, quantitatively analyze the response relationship between the changes of river water levels and pipe network liquid levels based on the monitoring data and correct the topological relationship between the pipe network and the river channel; The numerical model establishment module is used to construct an integrated numerical model of pipe network - outfall - river channel of the drainage system by using the corrected topological relationship between the pipe network and the river channel, and then calibrate and verify the model parameters of the integrated numerical model of pipe network - outfall - river channel by using the monitoring data to obtain the verified integrated numerical model of pipe network - outfall - river channel; The spatio-temporal quantitative measurement module is used to perform spatio-temporal quantitative measurement on the urban water pollutant balance quantity by using the overall balance measurement result of regional water pollutants and the verified integrated numerical model of pipe network-outfall-river, and obtain the quantitative measurement result of the urban water pollutant balance, so as to complete the urban water pollutant balance measurement operation.

[0025] In summary, for a method and system for measuring the urban water pollutant balance of the present invention, first, a basic database of urban water pollutants is constructed. Then, based on the basic database of water pollutants, the sewage generation amount of each industry and the direct sewage discharge amount of plots are calculated respectively by using the pollution coefficient method and the proportional coefficient method, and the equivalent sewage treatment amount is measured by using the chemical mass and water volume balance equations. Next, the triangle diagram method is used to divide the flow curve to measure the amount of external water flowing into the pipe network, so as to perform an overall balance measurement on regional water pollutants and obtain the overall balance measurement result of regional water pollutants. Subsequently, in-situ control experiments are carried out on the drainage system and a multi-element monitoring system of pipelines and rivers is established for monitoring to obtain monitoring data. Then, the response relationship between the changes of river water level and pipe network liquid level is quantitatively analyzed according to the monitoring data, and the topological relationship between the pipe network and the river is corrected. Then, an integrated numerical model of pipe network-outfall-river of the drainage system is constructed by using the corrected topological relationship between the pipe network and the river. Then, the model parameters of the integrated numerical model of pipe network-outfall-river are calibrated and verified by using the monitoring data to obtain the verified integrated numerical model of pipe network-outfall-river. Finally, the spatio-temporal quantitative measurement of the urban water pollutant balance quantity is carried out by using the overall balance measurement result of regional water pollutants and the verified integrated numerical model of pipe network-outfall-river, and the quantitative measurement result of the urban water pollutant balance is obtained, so as to complete the urban water pollutant balance measurement operation. The present invention effectively realizes the function of accurately measuring the urban drainage system water pollutant balance by integrating the triangle diagram method, the in-situ observation method and the numerical model method. And through the in-situ control experiment on the drainage system and the multi-element monitoring system of pipelines and rivers, the pipe network topological structure can be corrected in time and the pipe network-river hydrodynamic numerical value can be calibrated and verified. This not only avoids the distortion of model debugging caused by incorrect pipe network structure, but also can better reflect the dynamic evolution process of water pollutants, which provides a new method for accurately quantitatively measuring the spatio-temporal changes of urban water pollution load under changing scenarios, and has important significance for guiding the accurate prevention and control of urban water pollution and the targeted treatment of water environment, and significantly improves the reliability of pollution source tracing under the complex urban water system.

[0026] The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the balance of urban water pollutants, characterized in that: It includes the following steps: Step A: Construct a basic database of water pollutants in the target city; Step B: Based on the basic database of water pollutants, use the pollution coefficient method and the proportional coefficient method to calculate the sewage generation volume of each industry and the direct sewage discharge volume of plots respectively, and use the chemical mass and water volume balance equations to measure the equivalent sewage treatment volume. Then, use the triangular graph method to divide the flow curve to measure the amount of external water flowing into the pipe network, so as to conduct an overall balance measurement of regional water pollutants and obtain the overall balance measurement result of regional water pollutants; Step C: Conduct in-situ control experiments on the drainage system and establish a multi-element monitoring system for pipelines and rivers for monitoring to obtain monitoring data. Then, quantitatively analyze the response relationship between the changes in river water levels and pipeline network liquid levels based on the monitoring data and correct the topological relationship between the pipeline network and the river; Step D: Use the corrected topological relationship between the pipeline network and the river to construct an integrated numerical model of the pipeline network-outfall-river for the drainage system. Then, use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of the pipeline network-outfall-river and obtain the verified integrated numerical model of the pipeline network-outfall-river; Step E: Use the overall balance measurement result of regional water pollutants and the verified integrated numerical model of the pipeline network-outfall-river to conduct spatio-temporal quantitative measurement of the balance volume of urban sewage production and discharge pollutants and obtain the quantitative measurement result of urban water pollutant balance, thus completing the operation of urban water pollutant balance measurement.

2. The urban water pollutant balance calculation method according to claim 1, wherein: Step A: Construct a basic database of water pollutants in the target city. The basic database of water pollutants includes static data and dynamic data. The static data includes the population scale data of the target city, land use area data, pipeline network vector data, river vector data, outfall data, and pump station data. The dynamic data includes the urban residential tap water sales volume, industrial and service water sales volume, special industry water sales volume, daily rainfall, online sewage monitoring data of enterprises with online monitoring, water use and drainage data of enterprises without online monitoring, urban sewage treatment plant sewage treatment volume, and the influent COD concentration of the sewage treatment plant. Among them, the urban residential tap water sales volume includes residential living water sales volume, non-residential living water sales volume, secondary water supply sales volume, and special hardship preferential water sales volume; The specific construction process of the basic database of water pollutants is formed by decomposing the dynamic data according to the water supply areas of waterworks and the drainage areas of sewage treatment plants and combining the population scale data and land use area data of each administrative unit in the target city.

3. A method for calculating the balance of urban water pollutants according to claim 2, characterized in that: Step B: Based on the basic database of water pollutants, use the pollution coefficient method and the proportional coefficient method to calculate the sewage generation volume of each industry and the direct sewage discharge volume of plots respectively, and use the chemical mass and water volume balance equations to measure the equivalent sewage treatment volume. Then, use the triangular graph method to divide the flow curve to measure the amount of external water flowing into the pipe network, so as to conduct an overall balance measurement of regional water pollutants and obtain the overall balance measurement result of regional water pollutants. The overall balance measurement result of regional water pollutants includes sewage generation volume, sewage treatment volume, direct sewage discharge volume, and the amount of external water flowing into the pipe network. The specific steps are as follows: Step B1: Calculate the sewage generation volume of each industry using the pollution coefficient method, where the sewage generation volume is equal to the product of the water consumption and the corresponding pollution coefficient; Step B2: Calculate the direct sewage discharge of each industry plot using the proportional coefficient method. Specifically, the direct sewage discharge of the plot is calculated by multiplying the plot product quantity by the direct discharge coefficient estimated based on the pipe network. Step B3: Measure the equivalent sewage treatment volume using the chemical mass and water volume balance equation. Specifically, measure the equivalent sewage treatment volume of the urban sewage treatment plant by using the chemical mass and water volume balance relationship of the water quality characteristic factors of the drainage system. The measurement process using chemical oxygen demand (COD) instead of water volume as the measurement factor and applying the chemical mass and water volume balance equation is shown in Formula (1). ， （1） Among them, is the total influent flow rate of sewage treatment plant under dry weather conditions, is the raw sewage volume, is the infiltration and inflow volume of external water including groundwater and surface water, , and are the concentration of water quality characteristic factors of total sewage, raw sewage and external water under dry weather conditions respectively; Step B4: Divide the flow curve using the triangle graph method to measure the amount of external water flowing into the pipe network. Specifically, divide the sewage pipe network outlet flow curve during the corresponding time period according to the chemical mass and water volume balance equation, and then arrange the daily flow values within the selected time period at the end of the sewage pipe network in ascending order to form an S-shaped curve.

4. A method for calculating the balance of urban water pollutants according to claim 3, characterized in that: Step C: Conduct in-situ control experiments on the drainage system and establish a multi-factor monitoring system for pipes and rivers for monitoring to obtain monitoring data. Then, quantitatively analyze the response relationship between the river water level and the pipe network liquid level changes based on the monitoring data and correct the topological relationship between the pipe network and the river. The specific steps are as follows: Step C1: Conduct in-situ control experiments on the drainage system. Specifically, use the control variable method to regulate the river water level and the pipe network liquid level respectively. The specific steps are as follows: Step C11: Control the river water level. Specifically, first turn on the river drainage pump station and lower the river water level, then adjust the pumping flow of the pump station and maintain the river water level. Next, turn off the pump station and monitor the slow process of the water level rising. Then, open the water replenishment gate and monitor the obvious process of the river water level rising. Subsequently, increase the opening of the gate and monitor the accelerated process of the water level rising. Step C12: Control the pipeline sewage lift pump station. Specifically, first turn off one sewage lift pump station, then turn off another sewage lift pump station. Next, turn off one sewage lift pump station, and then turn off all integrated pump stations. At the same time, monitor the change process of the pipeline liquid level. Step C13: Control the airbag blockage. Specifically, block the sewage interception pipes on both sides of the river using airbags and clarify the blockage points for blockage according to the actual situation. Then, divide the pipeline into two independent pipelines and monitor the change of the pipeline liquid level in each of the two pipelines under the superposition of the river water level control. Step C14: Control the pipeline branch. Specifically, block the connected pipelines using airbags, and then control the different diversion ports of the pipeline sections and separately monitor the change of the liquid level in different pipeline sections. Step C2: Establish a multi-factor monitoring system for pipes and rivers for monitoring. The multi-factor monitoring system for pipes and rivers specifically monitors the pipeline liquid level, river water level, diversion port flow, and video during the in-situ control experiment of the drainage system. The specific steps are as follows: Step C21: Monitor the pipeline liquid level and the river water level. Specifically, use pipeline liquid level gauges to monitor each target pipeline, and use river float water level gauges to monitor the upstream and downstream of each target river, and synchronously monitor the river water level near the sewage well. Step C22: Monitor the flow at the pipeline intersection. Specifically, install fixed flow meters on-site when encountering pipe network bifurcations. Step C23: Pipeline video monitoring. Use a closed-circuit television monitoring system to detect pipeline seepage anomalies through endoscopy.

5. The method for calculating the balance of urban water pollutants according to claim 4, characterized in that: Step D: Construct an integrated numerical model of the drainage system network-outfall-river using the corrected topological relationship between the pipeline network and the river. Then, use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of the network-outfall-river and obtain the verified integrated numerical model of the network-outfall-river. The specific steps are as follows. Step D1: Construct an integrated numerical model of the drainage system network-outfall-river using the corrected topological relationship between the pipeline network and the river. The integrated numerical model of the network-outfall-river includes a rainfall-runoff module, a pipe flow calculation module, a water quality module, and a real-time control module. Step D2: Use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of the network-outfall-river and obtain the verified integrated numerical model of the network-outfall-river. The calibration and verification indicators include the Nash efficiency coefficient NSE, the percentage bias PBIAS, and the ratio coefficient RSR of the root mean square error to the standard deviation of the observations. The Nash efficiency coefficient NSE is used to quantify the measurement accuracy of the integrated numerical model of the network-outfall-river by the relative magnitude of the residual variance and the variance of the measurement data. The percentage bias PBIAS is used to measure the average trend of the data deviating from the observed data. The ratio coefficient RSR of the root mean square error to the standard deviation of the observations is used to standardize the root mean square error by the standard deviation of the observed values.

6. A method for calculating the balance of urban water pollutants according to claim 5, characterized in that: The specific steps of Step D1 are as follows. Step D11: Construct a rainfall-runoff module. The rainfall-runoff module uses the Horton infiltration formula, as shown in Equation (2). （2） Among them, is the infiltration rate, is the stable infiltration rate, is the initial infiltration rate, is the rainfall time, is the decay constant; Step D12: Construct a pipe flow calculation module. The pipe flow calculation module uses the Saint-Venant equations of unsteady open-channel flow partial differential equations. The specific steps are as follows. Step D121: Establish the mass conservation equation and the momentum conservation equation, as shown in Equation (3). ， （3）； Among them, is the flow rate, is the cross-sectional area, is the acceleration due to gravity, is the horizontal angle, is the bed slope, is the conveying capacity; Step D122: Use the Manning formula to calculate the steady flow of the river, as shown in Equation (4). （4） Among them, is the roughness coefficient, is the hydraulic radius, is the bottom slope of the river channel; Step D13: Construct a water quality module. The water quality module uses a one-dimensional advection-diffusion model to calculate the advection-diffusion process of soluble and suspended substances in water, as shown in Equation (5). ， （5） wherein, is the concentration of the substance, is the diffusion time, is the average flow velocity of the river, is the spatial coordinate, is the convective-diffusion coefficient, is the first-order decay coefficient of the substance, and are empirical parameters of the convective-diffusion coefficient; Step D14: Construct a real-time control module. The real-time control module is used to control the gate and pump station scheduling operations in the drainage system and change the scheduling rules by setting the measured parameters to achieve water flow measurement.

7. A method for calculating the balance of urban water pollutants according to claim 5, characterized in that: The specific calibration and verification process of Step D2 is as shown in Equation (6). ， ， ；（6） Among them, is the number of simulated data, is the th measured value, is the average value of the measured values, is the th simulated value, is the average value of the simulated values.

8. A method for calculating the balance of urban water pollutants according to claim 5, characterized in that: Step E: Using the overall balance measurement results of regional water pollutants and the verified integrated numerical model of pipe network - outfall - river, conduct spatio - temporal quantitative measurement of the pollutant balance of urban water production and drainage, and obtain the quantitative measurement results of urban water pollutant balance, thereby completing the measurement operation of urban water pollutant balance. Specifically, make a time series of the obtained overall balance measurement results of regional water pollutants on a daily scale and use it as the input variable of the verified integrated numerical model of pipe network - outfall - river. Then, use the verified integrated numerical model of pipe network - outfall - river to reproduce and decompose the spatio - temporal process of the urban water production - drainage pollutant balance measurement as a whole, and obtain the spatio - temporal quantitative measurement results of the pollutant production and discharge processes under the urban water use - drainage process, so as to obtain the quantitative measurement results of urban water pollutant balance.

9. An urban water pollutant balance calculation system, the specific calculation process of the urban water pollutant balance calculation system is based on the urban water pollutant balance calculation method according to any one of claims 1-8, characterized in that: It includes a database construction module, an overall balance measurement module, a multi - element monitoring module, a numerical model establishment module, and a spatio - temporal quantitative measurement module. The database construction module is used to construct the basic database of urban water pollutants in the target city. The overall balance measurement module is used to calculate the sewage production of each industry and the direct sewage discharge of plots respectively by using the pollution coefficient method and the proportional coefficient method based on the basic database of water pollutants, and calculate the equivalent sewage treatment volume by using the chemical mass and water volume balance equations. Then, use the triangle graphical method to divide the flow curve to measure the amount of external water flowing into the pipe network, so as to conduct an overall balance measurement of regional water pollutants and obtain the overall balance measurement results of regional water pollutants. The multi - element monitoring module is used to conduct in - situ control experiments on the drainage system and establish a multi - element monitoring system for pipes - rivers for monitoring, so as to obtain monitoring data. Then, quantitatively analyze the response relationship between the changes in river water level and pipe network liquid level based on the monitoring data and correct the topological relationship between the pipe network and the river. The numerical model establishment module is used to construct an integrated numerical model of pipe network - outfall - river for the drainage system by using the corrected topological relationship between the pipe network and the river. Then, use the monitoring data to calibrate and verify the model parameters of the integrated numerical model of pipe network - outfall - river and obtain the verified integrated numerical model of pipe network - outfall - river. The spatio - temporal quantitative measurement module is used to conduct spatio - temporal quantitative measurement of the pollutant balance of urban water production and drainage by using the overall balance measurement results of regional water pollutants and the verified integrated numerical model of pipe network - outfall - river, and obtain the quantitative measurement results of urban water pollutant balance, thereby completing the measurement operation of urban water pollutant balance.

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