Overflow frequency control-oriented drainage system closure multiple calculation method and system

Abstract

The invention discloses an overflow frequency control-oriented drainage system closure multiple calculation method, which comprises the following steps of: firstly, acquiring multi-year rainfall data of a research area, and dividing rainfall events according to a certain time interval; arranging the rainfall events according to the maximum rainfall intensity or net rainfall intensity; secondly, according to the overflow frequency control requirement of the overflow port, the rainfall intensity or net rain intensity limit value corresponding to the overflow frequency reaching the standard is counted; then, determining a dry season flow reference value of the section of the overflow port; and finally, the rainfall intensity or net rain intensity limit value is divided by the dry season flow characteristic value, and the interception multiple required for reaching the standard is calculated. The method has application value in the scenes of quality and efficiency improvement and water body environment protection of drainage pipe network systems such as combined system drainage system transformation, rainwater and sewage mixed connection or misconnection pipeline improvement and the like. And establishing a quantitative relationship between the overflow frequency of the overflow port and the interception multiple, and calculating the interception multiple required by the overflow port for reaching the standard, thereby providing a decision basis for black and odorous water body treatment and water body environment protection.

Description

Technical Field

[0001] This invention belongs to the fields of municipal administration, environment and water conservancy, and specifically relates to a method and system for calculating the interception multiple of a drainage system for overflow frequency control. Background Technology

[0002] Wastewater interception is a fundamental means of controlling urban water pollution. The key to interception project design lies in scientifically determining the interception ratio. Currently, methods for calculating the interception ratio can be broadly categorized into four types: the optimal economic investment method, the population density correlation method, the hydraulic model simulation method, and the standard recommendation method.

[0003] The optimal economic investment method determines the interception ratio from the perspective of economic input and output. It optimizes the interception ratio by minimizing the sum of water pollution losses and engineering construction costs. This method relies on the accurate quantification of economic parameters, but estimating economic losses is often quite difficult.

[0004] The population density correlation method is a method for determining the interception ratio by analyzing the impact of regional population density on the interception effect. However, this method ignores hydrological characteristics and has limited applicability.

[0005] The hydraulic model simulation method uses a hydrological and hydraulic model to simulate and calculate the interception ratio. However, this method requires a large number of accurate parameters such as drainage networks and catchment areas, and there are simulation errors. The implementation process is also quite complicated.

[0006] In addition, some domestic and international standards and specifications provide suggested values ​​for interception ratios. For example, my country's "Outdoor Drainage Design Standard" stipulates that the interception ratio should range from 2 to 5.

[0007] In recent years, both domestic and international requirements for water environmental quality have become increasingly stringent, leading to the use of indicators such as overflow frequency to control overflow discharge outlets (or overflow points) during rainy days. However, none of these methods can meet the practical requirements for overflow frequency control. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method and system for calculating the interception multiple of a drainage system for overflow frequency control, which solves the problem that the existing technology cannot meet the practical requirements of overflow frequency control.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] The method for calculating the interception multiple of a drainage system for overflow frequency control includes the following steps:

[0011] Step 1: Obtain multi-year rainfall data and predicted future rainfall data for the study area, and divide rainfall events according to a certain time interval;

[0012] Step 2: Arrange the rainfall events according to their maximum rainfall intensity or net rainfall intensity;

[0013] Step 3: Based on the overflow frequency control requirements of the overflow outlet, calculate the rainfall intensity or net rainfall intensity limit corresponding to the overflow frequency meeting the standard;

[0014] Step 4: Determine the dry season flow characteristic value of the overflow outlet section;

[0015] Step 5: Divide the rainfall intensity or net rainfall intensity limit from Step 3 by the dry season flow characteristic value from Step 4 to calculate the interception multiple required to meet the standard.

[0016] In step 2, firstly, the maximum value of the rainfall intensity or net rainfall intensity of each rainfall event is calculated, and then the rainfall events or net rainfall events are sorted from largest to smallest according to the maximum value.

[0017] The net rainfall intensity process line at the sewage outlet or overflow outlet is calculated using the net rainfall calculation method. The maximum value of the rainfall intensity or net rainfall intensity of the rainfall event or net rainfall event is calculated using the highest time precision of the original rainfall data.

[0018] The net rainfall calculation method adopts either the runoff coefficient method or the initial loss and subsequent loss method.

[0019] In step 3, firstly, according to the overflow frequency control requirements of the overflow outlet, the critical values ​​of rainfall intensity or net rainfall intensity corresponding to the overflow frequency meeting the standard are statistically analyzed for each year; then, the statistical characteristic values ​​of the critical values ​​of rainfall intensity or net rainfall intensity for each year, including the predicted year, are statistically analyzed; finally, according to the reliability requirements of overflow outlet control, different numerical statistical characteristic values ​​of the critical values ​​are selected as the rainfall intensity or net rainfall intensity limits for overflow frequency control of the overflow outlet.

[0020] The numerical statistical characteristics of the critical values ​​of rainfall intensity or net rainfall intensity corresponding to the overflow frequency reaching the standard under different combinations of years.

[0021] The specific process of step 4 is as follows:

[0022] The maximum or average flow rate of the discharge outlet or overflow outlet section during the dry season is determined by the measured flow process line method; based on the reliability requirements of overflow outlet control, different numerical statistical characteristic values ​​of the dry season flow rate are selected as the benchmark value of the dry season flow rate.

[0023] If dry season flow data is not readily available, the average or maximum dry season flow can be estimated using methods that estimate total population or population density.

[0024] The statistical characteristic values ​​include the maximum value and the average value.

[0025] A drainage system interception ratio calculation system for overflow frequency control is provided. The system includes a processor that uses the method described above to calculate the drainage system interception ratio, providing reference data for practical engineering projects.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention proposes a method for calculating the interception multiple to meet the control requirements such as the frequency of overflow at sewage outlets during rainy days. This method has application value for improving the quality and efficiency of drainage pipe network systems and protecting water bodies, such as the renovation of combined sewer systems and the rectification of mixed or misconnected rainwater and sewage pipes.

[0028] 2. This invention can establish a quantitative relationship between the overflow frequency of overflow outlets and the interception ratio, calculate the interception ratio required for overflow outlets to meet standards, and provide a basis for decision-making in the treatment of black and odorous water bodies and the protection of water environment.

[0029] 3. In the process of calculating the interception ratio, the critical value of rainfall intensity (net rainfall intensity) and the random variation of flow during the dry season are taken into account. The appropriate interception ratio can be selected based on the reliability requirements of overflow outlet control and the project budget. Attached Figure Description

[0030] Figure 1 This invention provides a calculation process for the interception multiple of a drainage system for overflow frequency control. Figure 1 .

[0031] Figure 2 This invention provides a calculation process for the interception multiple of a drainage system for overflow frequency control. Figure 2 . Detailed Implementation

[0032] The structure and working process of the present invention will be further described below with reference to the accompanying drawings.

[0033] To address the practical problems raised in the background art, this solution discloses a method for calculating the interception multiple of a drainage system for overflow frequency control, including the following steps:

[0034] Step 1: Obtain multi-year rainfall data for the study area and divide rainfall events according to a certain time interval;

[0035] Step 2: Arrange the rainfall events according to their maximum rainfall intensity or net rainfall intensity;

[0036] Step 3: Based on the overflow frequency control requirements of the overflow outlet, calculate the rainfall intensity or net rainfall intensity limit corresponding to the overflow frequency meeting the standard;

[0037] Step 4: Determine the baseline value of the dry season flow rate at the overflow outlet cross-section;

[0038] Step 5: Divide the rainfall intensity or net rainfall intensity limit from Step 3 by the dry season flow characteristic value from Step 4 to calculate the interception multiple required to meet the standard.

[0039] This method is based on rainfall data from a meteorological monitoring station in a Chinese city from 2007 to 2017 (January 1, 2008 to December 31, 2017), with a data temporal resolution of 5 minutes. The minimum rainfall event interval (MIET) was calculated to be 3 hours, and the original rainfall sequence was divided into 694 independent rainfall events. The statistical results are shown in Table 1. The study set an annual average overflow frequency control standard of 5 times and determined the average sewage flow rate during the dry season to be 0.4 mm / min.

[0040] Table 1. Statistics on Rainfall Events

[0041]

[0042] Specific Implementation Example 1, such as Figure 1 As shown.

[0043] The method for calculating the interception multiple of a drainage system for overflow frequency control includes the following steps:

[0044] The first step is to classify rainfall events based on multi-year rainfall data (or including predicted rainfall data) for the study area. The classification of rainfall events must ensure their independence. The minimum interval between two rainfall events can be selected based on the catchment time of the intercepting well (or overflow well) under study, or determined based on the catchment time of the drainage area (or watershed) under study.

[0045] The second step is to calculate the maximum value of the rainfall intensity (or net rainfall intensity) for each rainfall event. Based on this maximum value, the rainfall events (or net rainfall events) are sorted from largest to smallest on an annual basis. If possible, net rainfall calculation methods (such as the runoff coefficient method, initial loss and subsequent loss method, etc.) can be used to calculate the net rainfall intensity process line at the sewage outlet (or overflow outlet). Using the highest time precision of the original rainfall data (such as 1 minute, 5 minutes, etc.) as the unit, calculate the maximum value of the rainfall intensity (or net rainfall intensity) for each rainfall event (or net rainfall event).

[0046] The third step is to calculate the critical rainfall intensity (or net rainfall intensity) values ​​corresponding to the overflow frequency control requirements of the overflow outlet (such as the average number of overflows per year) for each year (including predicted years). Then, calculate the critical rainfall intensity (or net rainfall intensity) values ​​(such as the maximum value, average value, etc.) for each year. Based on the reliability requirements of overflow outlet management, select different numerical statistical characteristic values ​​of the critical values ​​(such as the maximum value, average value, etc.) as the rainfall intensity (or net rainfall intensity) limits for overflow frequency control of the overflow outlet.

[0047] Step 4: Determine the maximum (or average) dry season flow rate at the discharge outlet (or overflow outlet) cross-section (or the end cross-section of the upstream combined sewer system, or the upper cross-section of the downstream intercepting sewer) using the measured flow process line method. If dry season flow rate data is not readily available, the average (or maximum) dry season flow rate can be estimated using population or population density estimation methods. Based on the reliability requirements of overflow outlet control, select different statistical characteristic values ​​of the dry season flow rate (such as maximum, average, etc.) as the baseline value for the dry season flow rate.

[0048] The fifth step is to divide the rainfall intensity (or net rainfall intensity) limit from the third step by the dry season flow baseline value from the fourth step to calculate the interception multiple required to meet the standard.

[0049] Specifically, this case study is based on statistical rainfall events. After the original rainfall sequence was divided, a total of 694 independent rainfall events were obtained. The rainfall events for each year were sorted in descending order, and the top 5 rainfall events in the descending order for each year were selected for statistical analysis. The statistical results are shown in Table 2.

[0050] Table 2 Rainfall Intensity Sequence for Each Year

[0051]

[0052] Based on the data in Table 2 and the reliability requirements for overflow control, the maximum and average critical values ​​are 1.98 mm / min and 1.14 mm / min, respectively. These maximum and average critical values ​​are denoted as i1, representing the rainfall intensity (or net rainfall intensity) limits for overflow frequency control. Substituting these values ​​into the interception multiple formula, the interception multiple n is obtained. 01 The values ​​are 4.95 and 2.85.

[0053] Specific embodiment two, such as Figure 2 As shown.

[0054] This embodiment describes a method for calculating the interception multiple of a drainage system for overflow frequency control, including the following steps:

[0055] (1) Based on multi-year rainfall data (or including predicted rainfall data) of the study area, rainfall events are divided. The division of rainfall events should ensure the independence of the rainfall events. The minimum interval between two rainfall events can be selected based on the catchment time of the intercepting well (or overflow well) under study, or it can be determined based on the catchment time of the drainage area (or watershed) under study.

[0056] (2) Calculate the maximum value of rainfall intensity (or net rainfall intensity) for each rainfall event. Based on this maximum value, sort all rainfall events (or net rainfall events) from largest to smallest. If conditions permit, net rainfall calculation methods (such as runoff coefficient method, initial loss and subsequent loss method, etc.) can be used to calculate the net rainfall intensity process line at the sewage outlet (or overflow outlet). Calculate the maximum value of rainfall intensity (or net rainfall intensity) for each rainfall event (or net rainfall event) using the highest time precision of the original rainfall data (such as 1 minute, 5 minutes, etc.).

[0057] (3) Based on the overflow frequency control requirements of the overflow outlet (such as the number of overflows over many years), and on the basis of the sorting in step (2), perform sliding statistics on the numerical statistical characteristic values ​​(such as maximum value, average value, etc.) of the critical values ​​of rainfall intensity (or net rainfall intensity) corresponding to the overflow frequency meeting the standard under different year combinations. According to the reliability requirements of overflow outlet control, select different numerical statistical characteristic values ​​(such as maximum value, average value, etc.) of the critical values ​​as the rainfall intensity (or net rainfall intensity) limit for overflow frequency control of the overflow outlet.

[0058] (4) Determine the maximum (or average) dry season flow rate at the cross-section of the sewage outlet (or overflow outlet) (or the end cross-section of the upstream combined sewer system or the upper cross-section of the downstream intercepting sewer) using the measured flow process line method. If dry season flow rate data is not readily available, the average (or maximum) dry season flow rate can be estimated using population or population density estimation methods. Based on the reliability requirements of overflow outlet control, select different statistical characteristics of the dry season flow rate (such as maximum, average, etc.) as the baseline value for the dry season flow rate.

[0059] (5) Divide the rainfall intensity (or net rainfall intensity) limit in step (3) by the dry season flow baseline value in step (4) to calculate the interception multiple required to meet the standard.

[0060] Specifically, this case study is based on statistical rainfall data. After the original rainfall sequence was divided, a total of 694 independent rainfall events were obtained. The rainfall intensity of each rainfall event was arranged in descending order. The 50th rainfall intensity value was used as the rainfall intensity (or net rainfall intensity) limit for overflow frequency control at the overflow outlet, denoted as i2. The top 50 events with the highest rainfall intensity are detailed in Table 3.

[0061] Table 3. Ranking of the top 50 events with the highest rainfall intensity

[0062]

[0063] According to the statistical data in Table 3, the 50th rainfall intensity value, i2, is 1.02 mm / min. Substituting this rainfall intensity (or net rainfall intensity) limit i2 into the interception ratio formula, the interception ratio n can be calculated. 02 The value is 2.55.

[0064] From the above embodiments, it can be seen that:

[0065] 1. This scheme proposes a method for determining the minimum interval between rainfall events for overflow frequency control. That is, the minimum time interval between rainfall events is determined based on the water collection time of the interception well (or overflow well) to ensure the independence of rainfall events.

[0066] 2. A method for determining the limit value of rainfall intensity (or net rainfall intensity) is proposed. That is, based on the overflow frequency control requirements, the maximum rainfall intensity (or net rainfall intensity) of rainfall events is ranked, and the critical value of rainfall intensity (net rainfall intensity) required for the overflow outlet to meet the standard and its numerical statistical characteristics are statistically analyzed.

[0067] 3. In the process of calculating the interception ratio, the critical value of rainfall intensity (net rainfall intensity) and the random variation of flow during the dry season are taken into account. The appropriate interception ratio can be selected based on the reliability requirements of overflow outlet control and the project budget.

[0068] When this method is used in drainage systems designed for overflow frequency control, the calculated interception ratio is the minimum interception ratio required to meet overflow frequency standards. A higher interception ratio can also meet overflow frequency standards, but the investment will increase accordingly. In practical engineering applications, an appropriate interception ratio can be selected based on the project's investment budget.

[0069] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0070] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0071] Those skilled in the art should understand that variations can be implemented by combining existing technology and the above embodiments. Such variations do not affect the substantive content of this solution and will not be elaborated here.

[0072] It should be understood that this solution is not limited to the specific embodiments described above. Devices and structures not described in detail herein should be understood as being implemented in a manner common to the art. Any person skilled in the art can make many possible variations and modifications to this solution, or modify it into equivalent embodiments, without departing from the scope of this solution, using the methods and techniques disclosed above. This does not affect the substantive content of this solution. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this solution, without departing from its scope, still fall within the protection scope of this solution.

Claims

1. A method for calculating the interception multiple of a drainage system oriented to the control of overflow frequency, characterized in that: The method comprises the following steps: Step 1, obtaining multi-year rainfall data of a study area and predicting future rainfall data, and dividing rainfall events according to a certain time interval; Step 2, arranging the rainfall events according to the maximum rainfall intensity or the net rainfall intensity; Step 3, according to the overflow frequency control requirement of the overflow port, counting the rainfall intensity or net rainfall intensity limit value corresponding to the overflow frequency standard; Step 4, determining the dry season flow characteristic value of the overflow port section; Step 5, dividing the rainfall intensity or net rainfall intensity limit value in step 3 by the dry season flow characteristic value in step 4 to calculate the required interception multiple.

2. The method according to claim 1, wherein the method is characterized in that: In step 2, first, calculate the maximum value of the rainfall intensity or net rainfall intensity of each rainfall event, and then arrange the rainfall events or net rainfall events from large to small according to the maximum value.

3. The method according to claim 2, wherein the method is characterized by: The net rainfall calculation method is used to calculate the net rainfall intensity hydrograph at the sewage outlet or overflow port, and the maximum value of the rainfall intensity or net rainfall intensity of the rainfall event or net rainfall event is calculated in the highest time precision unit of the original rainfall data.

4. The method according to claim 3, wherein the method is characterized in that: The net rainfall calculation method adopts the runoff coefficient method or the initial loss and subsequent loss method.

5. The method according to claim 1, wherein the method is characterized in that: In step 3, first, according to the overflow frequency control requirement of the overflow port, count the rainfall intensity or net rainfall intensity critical value corresponding to the overflow frequency standard of each year; then, count the statistical characteristic value of the rainfall intensity or net rainfall intensity critical value of each year including the predicted year; finally, according to the reliability requirement of the overflow port control, select different numerical statistical characteristic values of the critical value as the rainfall intensity or net rainfall intensity limit value of the overflow port overflow frequency control.

6. The method according to claim 5, wherein the method is characterized by: Sliding statistical numerical statistical characteristic value of rainfall intensity or net rainfall intensity critical value corresponding to overflow frequency standard under different year combination conditions.

7. The method according to claim 6, wherein the method is characterized by: The specific process of step 4 is as follows: The maximum value or average value of the dry season flow of the sewage outlet or overflow port section is determined by the measured flow process line method; according to the reliability requirement of the overflow port control, different numerical statistical characteristic values of the dry season flow are selected as the dry season flow reference value.

8. The method according to claim 7, wherein the method is characterized in that: If the dry season flow data is not easy to obtain, the dry season flow average value or maximum value is estimated by the population total or population density estimation method.

9. The method according to claim 7, wherein the method is characterized by: The statistical characteristic value includes the maximum value and the average value.

10. A drainage system interception multiple calculation system oriented to overflow frequency control, characterized in that: The system comprises a processor, which applies the method of any one of claims 1 to 9 to calculate the interception multiple of the drainage system, and provides reference data for actual engineering.

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