An accurate estimation method for external water inflow rate and inflow points of sewage pipe networks based on model prediction

Abstract

The present invention relates to a method for accurately estimating the external water inflow rate and inflow points of a sewage pipe network based on model prediction. By establishing a sewage pipe network model, it is possible to accurately estimate the river water inflow rate and inflow points entering the sewage pipe network, and obtain the dynamic changes in the external water inflow volume, avoiding the influence of the pumping station operation conditions when interpreting the readings of the pipe network flow meters, and providing a quantitative management tool for the external water investigation, operation, and maintenance of the sewage pipe network. Reducing the external water inflow is an important guarantee for ensuring the normal operation of the sewage pipe network. After reducing the external water in the sewage pipe network, the liquid level of the sewage pipe network can be lowered, preventing sewage overflow during the rainy season and reducing the occurrence of water environment pollutant events caused by sewage overflow. In addition, reducing the external water entering the sewage pipe network can also increase the actual sewage collection capacity of the sewage pipe network, increase the sewage pollutant concentration, and improve the sewage treatment efficiency of the urban sewage treatment plant. After the external water is blocked, the flow rate of the sewage pump station decreases significantly, and the sewage concentration increases significantly.

Description

Technical Field

[0001] The present invention relates to a method for accurately estimating the inflow volume and inflow points of external water into a sewage pipe network based on model prediction, and belongs to the field of municipal engineering. Background Art

[0002] External water intrusion is the main reason for the low efficiency of sewage pipe network operation. The entry of a large amount of external water causes the sewage pipe network to operate at a high water level for a long time, and it is extremely easy to cause sewage overflow during the rainy season, seriously affecting the water environment quality. The entry of external water also reduces the actual sewage collection capacity of the sewage pipe network, resulting in a decline in sewage collection efficiency and a decrease in sewage concentration. A large amount of low-concentration sewage containing external water also makes it difficult to improve the operation efficiency of sewage treatment plants.

[0003] The external water entering the sewage pipe network mainly includes sources such as river water, groundwater, and rainwater. In most areas, river water inflow is the main way of external water intrusion into the sewage pipe network. In the construction process of rainwater and sewage pipes in some cities, there are cases of wrong connection and mixed connection between rainwater and sewage pipes. When the river water level is high, the river water will enter the rainwater pipe through the rainwater discharge port, and then enter the sewage pipe through the wrong rain-sewage connection pipe. Finding the river water inflow points and reducing the entry of river water into the sewage pipe network are the main means to improve the operation efficiency of the sewage pipe network. Before finding the river water inflow points, it is necessary to accurately estimate the inflow volume of river water entering the sewage pipe network. However, there is currently a lack of relevant technical means to estimate the inflow volume of river water within a regional scope.

[0004] Installing flow meters in the main pipes of the sewage pipe network and directly measuring can obtain the total amount of sewage within the region. However, compared with the regional water consumption, it is still difficult to obtain the external water volume from the sewage flow measured by the flow meters. This is because the sewage flow measured by the flow meters will be affected by the operating conditions of sewage pumping stations. The pumping volume of the pumping stations will also affect the water level of the sewage pipe network, thereby changing the liquid level difference between the river water and the pipe network, and further changing the external water inflow volume. Due to the mutual influence relationship among the external water flow, the operating conditions of the pumping stations, the water consumption, the pipe network liquid level, and the river channel liquid level, it is difficult to accurately estimate the external water inflow volume of the sewage pipe network. At the same time, because the sewage is buried underground, it is quite difficult to accurately locate the inflow points of external water.

[0005] The present invention can accurately estimate the inflow volume of river water entering the sewage pipe network and accurately locate the inflow points by establishing a sewage pipe network model, providing an important tool for the efficient operation and maintenance of the sewage pipe network. Summary of the Invention

[0006] The object of the present invention is to address the problems existing in the above-mentioned prior art, namely, the problem of external water intrusion in the operation of sewage pipe networks and the lack of a quantitative definition method for the inflow rate and inflow points of external water. A definition method for defining the inflow rate of sewage pipe networks is proposed, that is, an accurate estimation method for the external water inflow rate and inflow points of sewage pipe networks based on model prediction.

[0007] The object of the present invention is achieved as follows. An accurate estimation method for the external water inflow rate and inflow points of sewage pipe networks based on model prediction, characterized by including the following steps:

[0008] (1) Investigate the external water inflow rate of the sewage pipe network within a certain area;

[0009] (1-1) Obtain the demographic data within the area. According to the per capita domestic water consumption in the area, the domestic water consumption in the area can be obtained;

[0010] (1-2) Obtain the distribution of the regional domestic water consumption within 24 hours. Select a typical residential community within the area and record the change in the total water meter reading within the community within 24 hours of a day to obtain the time change of the water consumption in the community;

[0011] (1-3) Retrieve the water consumption data of enterprises and institutions within the area and obtain the distribution of the water consumption within 24 hours of the units with relatively large water consumption as the distribution of the water consumption of enterprises and institutions within the entire area;

[0012] (1-4) Considering that not all of the water consumption can become sewage, the loss coefficient is estimated at 20% of the water consumption, and the groundwater infiltration is also considered at 20%. After the two are offset, the water consumption is within the reasonable range of the actual sewage volume;

[0013] For the case of a relatively large external water inflow rate, the sewage loss and the groundwater infiltration are relatively small compared to the external water inflow rate. Therefore, its value has a relatively small impact on the overall sewage flow;

[0014] (1-5) Install sewage flow and liquid level gauges in the main sewage pipeline in front of the regional sewage pumping station, and at the same time install liquid level gauges in the inspection wells with a deeper liquid level in the upstream main pipeline of the sewage pipeline network; according to the ground and the elevation of the bottom of the inspection well pipe, convert the measured liquid level into liquid surface elevation data;

[0015] (1-6) Establish a sewage pipe network flow model. The flow model equation is as follows:

[0016]

[0017]

[0018] Among them, equation (1) is used to calculate the instantaneous external water flow rate (Q 外水),h 上游 is the liquid level elevation of the upstream inspection well, h 泵前 is the liquid level elevation of the inspection well in front of the pump station inlet pipe. The calculation of the external water flow (Q 外水 ); The upstream liquid level (h 上游 ) is mainly affected by the liquid level of the influent river course. Its dynamic change can be not included in the sewage pipe network model, and its value can be obtained by measuring with a liquid level gauge;

[0019] The dynamic change of the liquid level in front of the pump (h 泵前 ) can be calculated by Equation (2), where Q 外水 is calculated by Equation (1), Q 家庭 and Q 工业 are obtained from steps (1-2) and (1-3), and Q 泵站 is obtained online by the flowmeter installed in front of the pump station;

[0020] (1-7) Estimation of model parameters. There are two parameters K inf and A in model equations (1) and (2) that need to be estimated. By comparing the predicted liquid level in front of the pump and the measured liquid level in front of the pump, the values of the two parameters K inf and A are obtained. The measurement data is divided into two parts. One part is used for the estimation of the two model parameters, and the remaining data is used to verify whether the obtained model parameters can accurately predict the measured values. When the deviation between the measured values and the predicted values is within 5%, it can be considered that the estimation of the model parameters meets the accuracy requirements;

[0021] (1-8) Using the estimated model parameter values, and measuring the upstream and liquid levels in front of the pump, estimate the external water inflow according to Equation (1);

[0022] (2) Location of the external water inflow point;

[0023] (2-1) Analyze and summarize the existing sewage pipe network data, including its topological structure, the location of pipe points of inspection wells, the length, diameter, pipe bottom elevation and pipe well depth of pipelines, etc.;

[0024] (2-2) According to the sewage pipe network data, judge whether it is necessary to simplify the pipe network pipelines before establishing the pipe network mathematical model. When the pipe network data is relatively complete, in good agreement with the actual situation, and the scope of the pipe network survey area is small, that is, the area is less than 10 square kilometers, the pipe network survey data can be directly used for modeling;

[0025] (2-3) When the pipe network data is imperfect, there are some missing pipe points and pipe segments in the pipe network survey data, or the survey area is large, it is necessary to conduct on-site investigations to rationally supplement and simplify the existing pipe network data to meet the needs of model operation;

[0026] (2-4) Sub-region division is carried out on the surveyed area according to the sewage collection scope of the branch pipes of different sewage pipe networks to ensure that the sewage within the sub-region flows into the nearby sewage pipe network nodes nearby;

[0027] (2-5) Import the pipe points, pipeline, the depth of pipe points, the elevation of pipe bottoms, the diameter length, slope, pipe diameter and pipe material information in the pipe network surveying and mapping data or simplified sewage pipe network data, and the drainage information of water users within the sub-region into the GIS operation software;

[0028] (2-6) After the GIS information operation is completed, import it into the sewage pipe network simulation software EPA SWMM5.0 to establish a sewage pipe network mathematical model;

[0029] (2-7) Allocate the above calculated external water inflow values to different sewage pipe network nodes and operate the sewage pipe network mathematical model;

[0030] (2-8) Calculate the hydraulic state of the sewage pipe network under the conditions of external water inflow at different pipe network nodes, and compare it with the actual hydraulic state of the sewage pipe network to determine the calculated hydraulic state that is consistent with the actual hydraulic state of the sewage pipe network;

[0031] (2-9) Take the pipe network inflow nodes corresponding to the calculated hydraulic state obtained in step (2-8) as the calculated external water inflow points;

[0032] (2-10) Conduct on-site inspection of external water inflow at the calculated external water inflow points. After confirming the external water inflow points, the calculated external water inflow points can be considered as the actual external water inflow points, and the search for external water inflow points ends.

[0033] The method of the present invention is advanced and scientific. By establishing a sewage pipe network model, it can accurately estimate the river water inflow and inflow points entering the sewage pipe network, and obtain the dynamic changes of the external water inflow volume, avoiding the influence of the pumping station operation conditions when interpreting the readings of the pipe network flow meters, and providing a quantitative management tool for the external water investigation, operation and maintenance of the sewage pipe network.

[0034] Reducing the entry of external water is an important guarantee for ensuring the normal operation of the sewage pipe network. After reducing the external water in the sewage pipe network, the liquid level of the sewage pipe network can be reduced, preventing sewage overflow during the rainy season and reducing the occurrence of water environment pollutant incidents caused by sewage overflow. In addition, reducing the entry of external water into the sewage pipe network can also increase the actual sewage collection capacity of the sewage pipe network, improve the sewage pollutant concentration, and enhance the sewage treatment efficiency of the urban sewage treatment plant. After the external water is blocked, the flow rate of the sewage pump station decreases significantly and the sewage concentration increases significantly. Description of the Drawings

[0035] Figure 1 It is a schematic diagram of the external water inflow estimation process;

[0036] Figure 2 Per capita water consumption graph for each moment in the corresponding area of the embodiment;

[0037] Figure 3 Curve fitting for the sewage pipe network model in the embodiment;

[0038] Figure 4 Model parameters obtained by curve simulation in the embodiment (19000 (m 2.5 / d) and 2100 (m 2 )) and the graph of the external water volume result for this period calculated by the pipe network model;

[0039] Figure 5 Layout diagram of pipe points and pipelines in the service area of Hongxi Road Pumping Station in Yangzhou City in the embodiment;

[0040] Figure 6 Estimation area map of external water inflow points in the embodiment;

[0041] Figure 7 Simulation result graph of sewage flow state in the sewage pipe network in the service area of Hongxi Road Pumping Station on sunny days under the condition of external water intrusion in the embodiment;

[0042] Figure 8 Graph showing that the daily cumulative flow of the sewage pumping station has mostly decreased before and after the external water inflow point is blocked;

[0043] Figure 9 Graph showing that the sewage concentration in the pump station sump has increased significantly before and after the external water is blocked. Detailed implementation manners

[0044] The present invention will be further described below in conjunction with the accompanying drawings and the description of the drawings.

[0045] Taking the sewage collection range of Hongxi Road Sewage Pumping Station in Yangzhou City as an example, the detailed implementation manners of the present invention are described as follows:

[0046] (1) External water inflow estimation process;

[0047] 1. The area of this region is 6 square kilometers, with a permanent population of 25,000 people. Calculated according to the per capita domestic water consumption of 140 liters / day, the domestic water consumption in this region is 3500 tons / day.

[0048] 2. Investigate the 24-hour water consumption changes of 5 typical residential communities A, B, C, D, and E in this region. Record the reading changes of the total water meters of each community every hour within 24 hours. According to the permanent population numbers of each community, obtain the per capita water consumption at each moment of the 5 communities, and take the average of the 5 communities to obtain the per capita water consumption at each moment in this region, as shown in Figure 1 ;

[0049] 3. Retrieve the water consumption data of enterprises and institutions within the scope of this area, and obtain the water consumption distribution within 24 hours of the 5 units with relatively large water consumption, namely F, G, H, I, and J, as the water consumption distribution of enterprises and institutions within the entire area.

[0050] 4. Considering water loss and reasonable groundwater infiltration, the reasonable range of the sewage volume generated by domestic sewage and the water use of enterprises and institutions, including domestic sewage and the sewage volume generated by the water use of enterprises and institutions, is determined to be about 5000 tons.

[0051] 5. Install sewage flow and liquid level meters on the main sewage trunk pipeline in front of the regional sewage pumping station. At the same time, install liquid level meters in the inspection wells with deeper liquid levels in the upstream main pipeline of the sewage pipeline network. During the dry season, continuously monitor the liquid level and flow for 36 hours.

[0052] 6. Use the online monitoring and flow data obtained in step 5 to perform curve fitting using the above sewage pipeline network model.

[0053] 7. The results of the curve simulation are used for the estimation of the model parameters K inf and A, and their estimated values are 19000 (m 2.5 / d) and 2100 (m 2 ), respectively. Figure 3 This is the result of the curve simulation.

[0054] 8. Using the model parameters (19000 (m 2.5 / d) and 2100 (m 2 )) obtained from the curve simulation and the pipeline network model, the external water volume during this period can be calculated, and the calculation results are as Figure 4 shown.

[0055] (2) Process for locating the external water inflow point;

[0056] 1. Analyze the pipeline network topology of the area. In the preliminary work of the pipeline network management department, a pipeline network survey has been conducted on the sewage pipeline network, including the locations of pipe points (inspection wells), the lengths, diameters, pipe bottom elevations, and depths of pipe wells of the pipelines. The layout of pipe points and pipelines is shown in the following figure. After the sewage in the area is collected by the pipeline network, it enters the Hongxi Road sewage lift pump station in the lower right corner of the following figure, then enters the main sewage pipeline, and finally enters the Yangzhou Tangwang Sewage Treatment Plant;

[0057] 2. There are some missing pipe points and pipe segments in the pipeline network survey data of this area, and the existing pipeline network survey data cannot be directly used for modeling. It is necessary to conduct on-site investigations to reasonably supplement the existing pipeline network data to meet the needs of model operation;

[0058] 3. While supplementing the pipeline network data according to the current situation of the pipeline network, the pipeline network will be simplified to establish the Figure 6 simplified pipeline network model shown in Figure 6 (left side).

[0059] 4. As shown Figure 6 in the figure, the entire service area of Hongxilu Pumping Station is divided into 7 sub - areas. 55 major water users (residential communities, enterprises and institutions) within the area are assigned to the corresponding sub - areas according to their geographical locations. According to the pipe network survey data and on - site investigation, the sewage pipe network is simplified into 9 pipe points and 8 pipelines. Information such as the depth of the pipe points, the elevation of the pipe bottom, the diameter length, the slope, the pipe diameter and the pipe material is determined according to the survey data. The wastewater discharged from the water users within the sub - areas is discharged into the corresponding pipe points, and the pipe point (Out1) of the simplified pipe network is connected to Hongxilu Pumping Station.

[0060] 5. The division of sub - areas in the region, the import of water user, pipe point and pipeline information, etc. are completed within the QGIS operation software;

[0061] 6. After the GIS operation is completed, the file is imported into the sewage pipe network simulation software EPA SWMM5.0 for simulation (the right figure in the upper figure). In this study, the water user data obtained is the daily average water use data. To obtain the dynamic water use change data, 5 typical water users are selected to measure their dynamic water use data within 24 hours.

[0062] 7. According to the calculation results of the aforementioned external water volume, under the normal operation of Hongxilu Pumping Station on sunny days, the external water entering the regional sewage pipe network is between 15,000 - 20,000 tons. According to the previous pipe network detection situation, the integrity of the pipe network in this area is relatively good. Without considering the external water entering the sewage pipe network at multiple points for the time being, it is first considered that the external water enters the sewage pipe network concentratedly from a certain position. The J1 inspection well with a relatively high liquid level elevation is selected as the external water inflow point, and the operation of the sewage pipe network is simulated according to the external water inflow of 15,000 tons per day.

[0063] 8. If the simulation results deviate greatly from the actual situation, replace the external water inflow point and re - conduct the simulation. Figure 7 This is the simulation result of the sewage flow pattern in the sewage pipe network of the service area of Hongxilu Pumping Station under the condition of external water intrusion. Under the condition of an external water inflow of 15,000 tons per day, even on sunny days, and when the pump station flow is 0.22 cubic meters per second (19,000 tons per day), far exceeding the water use of 5,000 tons per day, the sewage pipe network is still in full - pipe flow, which is consistent with the current situation of the sewage pipe network in the service area of Hongxilu Pumping Station.

[0064] 9. Obtain the pipe network inflow node corresponding to the calculated hydraulic state in step 8 as the calculated external water inflow point;

[0065] 10. Conduct on - site external water inflow investigation at the calculated external water inflow point. After confirming the external water inflow point, the calculated external water inflow point can be considered as the actual external water inflow point, and the search for the external water inflow point ends.

Claims

1. An accurate estimation method for the external water inflow rate and inflow points of a sewage pipe network based on model prediction, characterized in that The steps include the following: (1) Investigate the inflow of external water into the sewage pipe network within a certain area; (1-1) Obtain the demographic data of the area. According to the per capita domestic water consumption in the area, the domestic water consumption in the area can be obtained; (1-2) Obtain the distribution of the domestic water consumption in the area within 24 hours. Select typical residential communities in the area and record the changes in the total water meter readings in the community within 24 hours of a day to obtain the time variation of the water consumption in the community; (1-3) Retrieve the water consumption data of enterprises and institutions within the area and obtain the distribution of the water consumption within 24 hours of the units with relatively large water consumption as the distribution of the water consumption of enterprises and institutions in the whole area; (1-4) Considering that not all of the water consumption can become sewage, the loss coefficient is estimated at 20% of the water consumption, and the groundwater infiltration is also considered at 20%. After the two are offset, the water consumption is within the reasonable range of the actual sewage volume; In the case of a relatively large inflow of external water, the sewage loss volume is relatively small compared with the groundwater infiltration volume and the inflow of external water. Therefore, its value has little impact on the overall sewage flow; (1-5) Install sewage flow and liquid level meters in the main sewage pipeline in front of the regional sewage pumping station. At the same time, install liquid level meters in the inspection wells with deeper liquid levels in the upstream main pipeline of the sewage pipeline network; according to the ground and the elevation of the bottom of the inspection well pipe, convert the measured liquid level into liquid surface elevation data; (1-6) Establish a sewage pipe network flow model. The flow model equation is as follows: Among them, Equation (1) is used to calculate the instantaneous external water flow rate (Q 外水 ), h 上游 is the liquid level elevation of the upstream inspection well, h 泵前 is the liquid level elevation of the inspection well in front of the intake pipe of the pumping station, and the calculation of the external water flow rate (Q 外水 ); the upstream liquid level (h 上游 ) is mainly affected by the liquid level of the inflow river, and its dynamic change can not be included in the sewage network model, and its value can be obtained by measuring with a liquid level gauge; The dynamic change of the liquid level (h 泵前 ) before the pump can be calculated by Equation (2), where Q 外水 is calculated by Equation (1), Q 家庭 and Q 工业 are obtained from Steps (1-2) and (1-3), and Q 泵站 is obtained online by the flowmeter installed in front of the pumping station; (1-7), Estimation of model parameters. There are two parameters K inf and A in the model equations (1) and (2) that need to be estimated. By comparing the predicted liquid level before the pump with the measured liquid level before the pump, the values of the two parameters K inf and A are obtained. The measurement data is divided into two parts. One part is used for the estimation of the two model parameters, and the remaining data is used to verify whether the obtained model parameters can accurately predict the measured values. When the deviation between the measured value and the predicted value is within 5%, it can be considered that the estimation of the model parameters meets the accuracy requirements; (1-8) Use the estimated model parameter values and the measured upstream and pre-pump liquid levels to estimate the inflow of external water according to equation (1); (2) Locate the points of external water inflow; (2-1) Analyze and summarize the existing sewage pipe network data, including its topological structure, the positions of the pipe points of the inspection wells, the length, diameter, elevation of the bottom of the pipe, and the depth of the pipe well, etc.; (2-2) According to the sewage pipe network data, judge whether it is necessary to simplify the pipe network pipeline and then establish a pipe network mathematical model. When the pipe network data is relatively complete, in good agreement with the actual situation, and the surveyed area of the pipe network is relatively small, that is, the area is less than 10 square kilometers, the pipe network survey data can be directly used for modeling; (2-3) When the pipe network data is imperfect, there are some missing pipe points and pipe segments in the pipe network survey data, or the surveyed area is relatively large, it is necessary to conduct on-site investigations to reasonably supplement and simplify the existing pipe network data to meet the needs of model operation; (2-4) According to the sewage collection scope of different branch pipes of the sewage pipe network, divide the surveyed area into sub-areas to ensure that the sewage within the sub-areas flows into the nearby sewage pipe network nodes nearby; (2-5) Import the pipe points, pipelines, the depth of the pipe points, the elevation of the bottom of the pipe, the diameter length, slope, diameter, and pipe material information in the pipe network survey data or the simplified sewage pipe network data, and the drainage information of the water users within the sub-areas into the GIS operation software; (2-6) After the GIS information operation is completed, import it into the sewage pipe network simulation software EPA SWMM5.0 to establish a sewage pipe network mathematical model; (2-7) Allocate the calculated value of the external water inflow to different sewage network nodes and operate the mathematical model of the sewage network; (2-8) Calculate the hydraulic state of the sewage network under the conditions of external water inflow at different network nodes, compare it with the actual hydraulic state of the sewage network, and determine the calculated hydraulic state that conforms to the actual hydraulic state of the sewage network; (2-9) Obtain the network inflow nodes corresponding to the calculated hydraulic state from step (2-8) and use them as the calculated external water inflow points; (2-10) Conduct on-site investigation of the external water inflow at the calculated external water inflow points. After confirming the external water inflow points, the calculated external water inflow points can be considered as the actual external water inflow points, and the search for the external water inflow points ends.

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