An assessment and analysis method for rainfall-induced infiltration in a pump sewage system

Abstract

The present invention discloses an evaluation and analysis method for the inflow and infiltration phenomenon caused by rainfall in a pump drainage sewage drainage system operating at a high liquid level, including: analysis and evaluation of the inflow and infiltration caused by rainfall in the overall sewage drainage system; quantitative evaluation of the inflow caused by rainfall in the overall sewage drainage system and each sub-region; positioning of the inflow in the overall sewage drainage system. The present invention forms an analysis and evaluation process and method for inflow and infiltration based on pipe network water quality / quantity data through the analysis of the online flow rate, water level, and conductivity data of the drainage system. The present invention can realize the analysis and evaluation of the inflow and infiltration operation state of the high liquid level drainage system based on perception data; can quantitatively evaluate the degree of inflow and infiltration of the high liquid level operating drainage system; and can roughly locate the location of the inflow and infiltration, facilitating the adoption of further measures.

Description

Technical Field

[0001] The present invention relates to the field of sewage drainage, and specifically relates to an evaluation and analysis method for the inflow and infiltration phenomenon caused by rainfall in a pump - type sewage drainage system operating at a high liquid level. Background Art

[0002] The drainage pipeline system is an important part of urban infrastructure, and is responsible for promptly discharging sewage and rainwater in the city to ensure urban safety and hygiene. With the process of urbanization, new pipe network systems are constantly being built, and problems with old pipelines are gradually emerging.

[0003] During the long - term use of drainage pipelines, due to the effects of sewage corrosion, erosion, scouring, sedimentation, and ground loads, and the need to continuously expand and transform the underground pipe network during the urban development stage, problems such as sewage pipeline breakage and rain - sewage misconnection are common in cities. Peng Zhongya et al. found in the investigation of an economic development zone in Jiangsu Province that there were 34 cases of rupture, disconnection, and misalignment in 14.6 km of pipelines (Research on Countermeasures for Improving the Quality and Efficiency of Urban Sewage Collection Systems - Taking Area A of a Wastewater Treatment Plant as an Example [J]. Water & Wastewater Engineering, 2020, 56(S1): 430 - 434 + 440). Zhang Funa et al. conducted an endoscopic inspection of old pipelines in a certain area of a southern city and found 240 structural defects in this area, with the main defects being branch pipe hidden connection, rupture, and foreign object penetration; for the newly built pipelines in this area, a total of 442 structural rigidity defects were found within 770 km, including 103 pipeline ruptures (Research on Countermeasures for Improving the Quality and Efficiency of the Sewage Collection System in a Southern Coastal City [D]. Harbin Institute of Technology, 2019. DOI: 10.27061 / d.cnki.ghgdu.2019.001528). When Li Lanjuan et al. inspected the rain - sewage pipelines in Shanghai, they found that there were as many as 20,290 mixed connection points in 19,000 km of separate - flow rain - sewage pipelines (Analysis of the Causes of Low Concentration of Inlet Water in Urban Sewage Treatment Plants in Southern China and Countermeasure Suggestions [C] / / Proceedings of the 2021 Annual Conference of the Chinese Society for Environmental Sciences - Sub - session of Environmental Engineering Technology Innovation and Application (I), 2021: 228 - 233 + 239. DOI: 10.26914 / c.cnkihy.2021.022150). A large number of pipelines are operating in a faulty state, making it very easy for external water bodies to enter the sewage pipeline system. Therefore, the problem of inflow and infiltration is widespread. Especially in the southern region with a high groundwater level and humid and rainy climate, the problem of inflow and infiltration is more serious.

[0004] The direct detection method of influent infiltration mainly aims to find the points where influent infiltration occurs. The commonly used methods are the smoke method and CCTV detection. At the same time, scholars at home and abroad have proposed various evaluation methods to evaluate the influent infiltration situation of sewage pipelines. Among them, comparing the flow rates on sunny and rainy days is the simplest and most direct method. However, for drainage systems operating at high levels, there is still a lack of evaluation methods for influent infiltration based on information data such as flow rate, water level, and water quality. Summary of the Invention

[0005] The present invention provides an evaluation and analysis method for the influent infiltration phenomenon caused by rainfall in a pump - drained sewage drainage system operating at a high level. Through the analysis of the online flow rate, water level, and conductivity data of the drainage system, an analysis and evaluation process and method for influent infiltration based on the water quality / quantity data of the pipe network are formed.

[0006] The specific technical solutions are as follows:

[0007] An evaluation and analysis method for the influent infiltration phenomenon caused by rainfall in a pump - drained sewage drainage system operating at a high level, the logical process is as Figure 1 shown, including:

[0008] 1) Analysis and evaluation of influent infiltration caused by rainfall in the overall sewage drainage system:

[0009] The main index for evaluating the influent infiltration phenomenon in the overall sewage drainage system is the flow rate Q of a single pump - starting event. If the flow rate Q of a single pump - starting event under working condition I I is less than the flow rate Q of a single pump - starting event under working condition II II , then there is an influent infiltration phenomenon caused by rainfall in the overall sewage drainage system; otherwise, the overall sewage drainage system is normal;

[0010] The flow rate of a single pump - starting event refers to the ratio of the total amount of water discharged by the pump station in the pump - starting event to the time it takes for the water level to drop from the initial value to the lowest value and then return to the initial value;

[0011] Working condition I is a condition of no rainfall for more than three consecutive days;

[0012] Working condition II is a rainfall condition;

[0013] 2) In the case where Q I is less than Q II , conduct analysis and evaluation of influent infiltration caused by rainfall in the overall sewage drainage system:

[0014] The main index for evaluating the influent infiltration phenomenon in the overall sewage drainage system is the rising rate R of the water level after the pump stops. If the rising rate R of the water level after the pump stops under working condition I I is less than the rising rate R of the water level after the pump stops under working condition III III, then there are both inflow and infiltration phenomena caused by rainfall in the overall sewage drainage system. Otherwise, there is only inflow caused by rainfall in the overall sewage drainage system;

[0015] The water level rising rate R after pump shutdown refers to the rising rate during the water level rising process after pump shutdown in the pump startup event;

[0016] Operating condition III is the condition where rainfall occurred within three days before the pump startup event and there is no rainfall during the pump startup process;

[0017] 3) Quantitative assessment of the inflow caused by rainfall in the overall sewage drainage system and each sub - area:

[0018] According to the pump station flow rate of the overall sewage drainage system and the flow rates of each sub - area, quantitatively determine the inflow caused by rainfall in the overall sewage drainage system and each sub - area:

[0019] RDI=(q II -q I ) / (I×S) (1),

[0020] In formula (1), RDI represents the inflow per unit area per unit rainfall, q II represents the flow rate in the pump startup event under operating condition II of the overall sewage drainage system or each sub - area, q I represents the flow rate in the pump startup event under operating condition I of the overall sewage drainage system or each sub - area, I represents the rainfall, and S represents the area of the overall sewage drainage system or each sub - area;

[0021] 4) Location of the inflow in the overall sewage drainage system:

[0022] 4 - 1) Under operating condition II, the overall sewage drainage system without pumps running is in a backwater state. Measuring points with a larger water level rising speed and rising amplitude indicate a larger rainwater inflow. Locate the inflow by the magnitude of the water level rising rate and rising amplitude:

[0023]

[0024] In formula (2):

[0025] 1, 2, …, n respectively represent each measuring point,

[0026] R Y1 ,R Y2 , …,R Yn respectively represent the water level rising rates of the corresponding measuring points caused by the rainfall peak,

[0027] H Y1 ,H Y2 , …,H Yn respectively represent the water level rising amounts of the corresponding measuring points caused by the rainfall peak,

[0028] i represents the measurement point with the largest influent flow;

[0029] 4-2) In the case of no pump running, the change in conductivity is used as the positioning index for influent flow. If the maximum decline rate of the conductivity at a certain measurement point reaches more than 20% during a rainfall event, it is considered that there is rainwater influent at this measurement point; otherwise, it is considered that there is no rainwater influent at this measurement point.

[0030] The inventor's research found that there is a large gap between the assessment of influent and infiltration in a pumped sewage drainage system and that in a gravity flow drainage system. Because the flow rate of the pumped system is mainly determined by the pump running duration and the pump flow rate, the system discharge flow rate has basically no regular pattern with the influent and infiltration phenomena caused by rainfall. Therefore, the traditional investigation and assessment method mainly based on flow rate is not applicable to the pumped system.

[0031] The influent and infiltration caused by rainfall mainly include direct influent during rainfall and infiltration caused by rainfall (indirect influent, that is, rainwater infiltrates into the underground pipeline from the pipeline rupture after infiltrating into the ground during rainfall). Direct influent often occurs during rainfall and the confluence time after rain, while indirect influent can often last for a period of time after rain. Therefore, in the data analysis method, the present invention divides the analysis working conditions into three categories: continuous non-rainfall working condition (working condition I), rainy day working condition (working condition II), and working condition with rainfall three days before the pump start event (working condition III).

[0032] Through water quality analysis, the present invention found that indicators such as TOC (total organic carbon) and COD (chemical oxygen demand) cannot well respond to the water quality change law between sunny and rainy days, while conductivity has a good response to the change between sunny and rainy days, and conductivity data is relatively easy to detect and can realize online monitoring. Therefore, the conductivity indicator can be used as the assessment indicator for influent and infiltration.

[0033] Compared with the prior art, the main advantages of the present invention include:

[0034] 1. The present invention can realize the analysis and assessment of the influent and infiltration operation status of a high-level drainage system based on perception data;

[0035] 2. The present invention can quantitatively evaluate the degree of influent and infiltration of a high-level operation drainage system;

[0036] 3. The present invention can roughly locate the location of influent and infiltration, which is convenient for taking further measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic logical flow diagram of the assessment and analysis method for the influent and infiltration phenomenon caused by rainfall in the pumped sewage drainage system with high-level operation of the present invention;

[0038] Figure 2Schematic diagram of the research area for the drainage system research case of the embodiment;

[0039] Figure 3 Instrument installation diagram of the research area for the embodiment. In the figure: The L series represents the flow measurement points, the Y series represents the liquid level measurement points, the R series represents the rainfall measurement points, and the D series represents the conductivity measurement points;

[0040] Figure 4 Schematic diagram of a single pump start event;

[0041] Figure 5 Drainage system flow rates under three types of pump start events for the research case of the embodiment;

[0042] Figure 6 Variations of the Y1 water level (1st water level) and Y2 water level (2nd water level) during a rainfall event on a certain day. In the figure, IR represents rainfall;

[0043] Figure 7 Relationship between the influent flow into Zone I of the drainage system and rainfall;

[0044] Figure 8 Relationship between the influent flow into Zone II of the drainage system and rainfall;

[0045] Figure 9 Conductivity variations of each measurement point during a rainfall event on a certain day. Specific implementation manners

[0046] The following further elaborates the present invention in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The operating methods without specific conditions noted in the following embodiments are generally in accordance with conventional conditions or in accordance with the conditions recommended by the manufacturer.

[0047] The evaluation and analysis method for the influent and infiltration phenomenon caused by rainfall in the pump - drained sewage drainage system operating at a high liquid level of the present invention has a logical flow as Figure 1 shown, including:

[0048] 1) Analysis and evaluation of the influent and infiltration caused by rainfall in the overall sewage drainage system:

[0049] The main index for evaluating the influent and infiltration phenomenon in the overall sewage drainage system is the flow rate Q of a single pump start event. If the flow rate Q of a single pump start event under operating condition I I is less than the flow rate Q of a single pump start event under operating condition II II , then there is an influent and infiltration phenomenon caused by rainfall in the overall sewage drainage system; otherwise, the overall sewage drainage system is normal;

[0050] The flow rate of a single pump start event refers to the ratio of the total amount of water discharged by the pump station during the pump start event to the time taken for the water level to drop from the initial value to the lowest value and then return to the initial value;

[0051] Operating condition I is the condition of no rainfall for more than three consecutive days, which can also be called the sunny period in this embodiment;

[0052] Operating condition II is the rainfall condition, which can also be called the rainy period in this embodiment;

[0053] 2) When Q I is less than Q II , analyze and evaluate the infiltration caused by rainfall in the overall sewage drainage system:

[0054] The main index for evaluating the infiltration phenomenon of the overall sewage drainage system is the water level rising rate R after the pump is stopped. If the water level rising rate R after the pump is stopped under operating condition I I is less than the water level rising rate R after the pump is stopped under operating condition III III , then there are both inflow and infiltration phenomena caused by rainfall in the overall sewage drainage system. Otherwise, there is only an inflow phenomenon caused by rainfall in the overall sewage drainage system; [[ID=2〕〕

[0055] The water level rising rate R after the pump is stopped refers to the rising rate during the process of the water level rising after the pump is stopped in the pump starting event;

[0056] Operating condition III is the condition that there was rainfall within three days before the pump starting event and no rainfall during the pump starting process, which can also be called there was rainfall within three days in this embodiment;

[0057] 3) Quantitative evaluation of the inflow caused by rainfall in the overall sewage drainage system and each sub - area:

[0058] According to the pump station flow rate of the overall sewage drainage system and the flow rates of each sub - area, quantitatively determine the inflow caused by rainfall in the overall sewage drainage system and each sub - area:

[0059] RDI=(q II - q I ) / (I×S) (1),

[0060] In formula (1), RDI represents the inflow per unit area per unit rainfall, q II represents the flow rate in the pump starting event under operating condition II of the overall sewage drainage system or each sub - area, q I represents the flow rate in the pump starting event under operating condition I of the overall sewage drainage system or each sub - area, I represents the rainfall, and S represents the area of the overall sewage drainage system or each sub - area;

[0061] 4) Location of the inflow in the overall sewage drainage system:

[0062] 4-1) Under operating condition II, the overall sewage drainage system without the pump running is in a state of backwater. Measuring points with a large water level rising speed and amplitude indicate a large inflow of rainwater. The inflow location is determined by the magnitude of the water level rising rate and amplitude:

[0063]

[0064] In formula (2):

[0065] 1, 2, …, n represent each measuring point respectively,

[0066] R Y1 , R Y2 , …, R Yn respectively represent the water level rising rates of the corresponding measuring points caused by the rainfall peak,

[0067] H Y1 , H Y2 , …, H Yn respectively represent the water level rising amounts of the corresponding measuring points caused by the rainfall peak,

[0068] i represents the measuring point with the largest inflow;

[0069] 4-2) Without the pump running, the change in conductivity is used as an index for inflow location. If the maximum decline rate of the conductivity at a certain measuring point during a rainfall event reaches more than 20%, it is considered that there is rainwater inflow at this measuring point; otherwise, it is considered that there is no rainwater inflow at this measuring point. The areas with relatively serious direct inflow can be analyzed through the conductivity ratio between sunny and rainy days. The larger the conductivity ratio, the more rainwater directly flows in at that place.

[0070] The following takes the service area of Pumping Station 1# (Dushan No. 1) in Dushan Town, Pinghu City as the research object. This area is located in Dushan Port Town, Pinghu City, Zhejiang Province. As Figure 2 shown, there is Huanggu Pond from west to southeast and Weiguo River from north to south nearby. The instrument installation in the research area is as Figure 3 shown. A schematic diagram of a pump-starting event is as Figure 4 shown.

[0071] Flow analysis:

[0072] By installing sensing devices and analyzing the sensing devices for water level, flow rate, water quality, etc., the discharge flow rates under three operating conditions are as Figure 5 shown.

[0073] In the first type of pump-starting event (sunny period), since there is no rainfall and the groundwater level is also at a relatively stable level, the water discharged by Dushan No. 1 Pumping Station can be considered as the collected domestic and industrial sewage and the infiltration of groundwater. Therefore, this part of the flow rate can be considered as the basic flow rate of the system.

[0074] In the second type of pump startup event (with rainfall within three days), due to the rainfall phenomenon in the early stage of pump startup, after the rainfall runoff infiltrates, the groundwater table will rise, which may lead to an increase in infiltration caused by rainfall (indirect inflow of rainfall). Therefore, the flow rate in this type of pump startup event may consist of base flow and groundwater infiltration flow.

[0075] In the third type of pump startup event (during rainy days), due to rainfall events occurring during the pump startup process, surface rainfall runoff will enter the sewage system through connections or other channels, forming an inflow phenomenon. Therefore, in this type of pump startup event, the discharged water volume includes not only the base flow but also the rainwater inflow volume.

[0076] Therefore, through the flow rate analysis of the three types of pump startup events, the inflow and infiltration conditions in the Dushan No. 1 drainage system can be evaluated.

[0077] Liquid level analysis:

[0078] Water level analysis is also an important way to analyze and evaluate inflow and infiltration. Therefore, based on the flow rate analysis, the present invention further analyzes the water level changes in the Dushan No. 1 pumping station.

[0079] From Figure 6 the water level changes in it, it can be seen that although the sub-drainage systems in Areas I and II are already operating at a high liquid level, under the action of rainfall, the water level still continues to rise. At the same time, with the appearance of the rainfall peak, the water level shows a rapid upward response. The greater the rainfall, the higher the water level rises. The response degree of the water level rise is almost synchronous with the change in rainfall intensity. This result further proves that there is an obvious direct rainwater inflow phenomenon in the Dushan No. 1 drainage system.

[0080] Quantitative analysis:

[0081] As Figure 7 , Figure 8 shown, the direct rainwater inflow volume in Drainage Sub-areas I and II increases with the increase in rainfall. According to the fitting formula, the direct rainwater inflow volume in Area I is about 4.79 m 3 / (h·mm), that is, for every mm of rainfall, about 4.79 m 3 / h of flow rate flows into the system. The direct rainwater inflow volume in Drainage Sub-area II is about 5.51 m 3 / (h·mm), that is, for every mm of rainfall, about 5.51 m 3 / h of flow rate flows into Sub-area II of the system.

[0082] Location analysis (pumping station not in operation):

[0083] Figure 9 is the change law of the conductivity of each water quality measurement point under the rainfall condition on a certain day. The total rainfall of this rainfall is 21.3 mm. FromFigure 9 It can be seen that after rainfall occurred, the conductivity at measuring point D1 decreased slowly, gradually dropping from approximately 2250 μS / cm to around 1500 μS / cm, indicating that there was a continuous inflow of rainwater at this point.

[0084] Similarly, there was also the same phenomenon of conductivity decrease at measuring point D4. At the peak moment of rainfall, the conductivity rapidly dropped from 1200 μS / cm to 800 μS / cm, indicating that rainwater directly flowed into this well from the nearby plot, resulting in the rapid decrease of conductivity.

[0085] From Figure 9 it can also be known that the conductivity at measuring points D2 and D3 did not change significantly before and after rainfall, basically remaining around 1500 μS / cm. Thus, it can be seen that there was no obvious phenomenon of direct rainwater inflow at these two measuring points under rainfall conditions.

[0086] From the water quality data, it can be known that there was a phenomenon of direct rainwater inflow under rainfall conditions at the positions of measuring points D1 and D4, while the phenomenon of rainwater inflow at measuring points D2 and D3 was basically negligible.

[0087] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. An evaluation and analysis method for the influent and infiltration phenomenon caused by a pump drainage sewage drainage system operating at a high liquid level under the action of rainfall, characterized in that, Including: 1) Analysis and assessment of the influent infiltration caused by rainfall in the overall sewage drainage system: The main index used to evaluate the inflow and infiltration phenomenon of the overall sewage drainage system is the flow rate Q of a single pump start event. The flow rate of a single pump start event refers to the ratio of the total water volume discharged from the pumping station during the pump start event to the time taken for the water level to drop from the initial value to the lowest value and then recover to the initial value. If the flow rate Q of a single pump start event under working condition I I is less than the flow rate Q of a single pump start event under working condition II II , then there is an inflow and infiltration phenomenon caused by rainfall in the overall sewage drainage system. Otherwise, the overall sewage drainage system is normal; Condition I is the condition of no rainfall for more than three consecutive days; Condition II is the rainfall condition; 2) In Q I Less than Q II In the case of, conduct an analysis and evaluation of the infiltration caused by rainfall in the overall sewage drainage system: The main index for evaluating the infiltration phenomenon of the overall sewage drainage system is the water level rising rate R after the pump is stopped. The water level rising rate R after the pump is stopped refers to the rising rate during the process of the water level rising after the pump is stopped in the pump start event. If the water level rising rate R after the pump is stopped under working condition I I is less than the water level rising rate R after the pump is stopped under working condition III III , then there are both inflow and infiltration phenomena caused by rainfall in the overall sewage drainage system. Otherwise, there is only an inflow phenomenon caused by rainfall in the overall sewage drainage system; Condition III is the condition where rainfall occurred within three days before the pump start event and there is no rainfall during the pump start process; 3) Quantitative assessment of the influent caused by rainfall in the overall sewage drainage system and each sub-region: According to the pump station flow rate of the overall sewage drainage system and the flow rates of each sub-region, quantitatively determine the influent volume caused by rainfall in the overall sewage drainage system and each sub-region: RDI = (q II - q I ) / (I × S) (1), In Equation (1), RDI represents the inflow per unit rainfall per unit area, and q II represents the flow rate in the pump start-up event under Condition II for the entire sewage drainage system or each sub-zone, and q I represents the flow rate in the pump start-up event under Condition I for the entire sewage drainage system or each sub-zone, I represents the rainfall, and S represents the area of the entire sewage drainage system or each sub-zone; 4) Location of the influent in the overall sewage drainage system: 4-1) Under Condition II, when the overall sewage drainage system without pumps is in a backwater state, the measuring points with a large water level rising speed and rising amplitude indicate a large amount of rainwater influent. The location of the influent is determined by the magnitude of the water level rising rate and rising amplitude: In formula (2): 1, 2, …, n respectively represent each measuring point, R Y1 , R Y2 , …, R Yn respectively represent the water level rising rates of the corresponding measuring points caused by the rainfall peaks H Y1 , H Y2 , …, H Yn respectively represent the water level rise amounts at the corresponding measuring points caused by the rainfall peaks. i represents the measuring point with the largest influent; 4-2) In the case of no pumps, the change in conductivity is used as the location index of the influent. If the maximum decline rate of the conductivity at a certain measuring point reaches more than 20% during the rainfall event, it is considered that there is rainwater influent at this measuring point; otherwise, it is considered that there is no rainwater influent at this measuring point.

Images