Method for calculating the clean water ratio in sewage pipes considering the self-oxidation of inflow clean water

Abstract

The present invention belongs to the technical field of sewage treatment, and specifically relates to a method for calculating the clean water ratio of a sewage pipeline considering the self-oxidizability of inflow clean water, comprising the following steps: establishing a reference curve for the influence of clean water inflow on the oxidation attenuation of pollutants in the service area of ​​the sewage pipe network; for the pipe section where the clean water inflow actually occurs, defining the upstream and downstream monitoring ranges of the clean water inflow point, and respectively measuring the concentrations of inlet and outlet pollutants; checking the type and source of the inflow clean water, measuring the ORP and pollutant concentration of the clean water; estimating the clean water ratio i of the sewage pipe network; measuring the average flow velocity v of the pipeline, and estimating the hydraulic retention time t in combination with the pipeline length s; determining the pollutant oxidation attenuation ratio γ according to i, ORP and t; and calculating the clean water ratio of the sewage pipe. The present invention incorporates the oxidation of pollutants and the self-attenuation of pollutants by the self-oxidizability of clean water into the calculation model based on chemical mass balance, which can improve the accuracy of the calculation result of the clean water ratio of the sewage pipe network.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and specifically relates to a method for calculating the clean sewage ratio of a sewage pipe by taking into account the oxidizability of the inflowing clean water itself. Background Art

[0002] Urban sewage pipe networks generally have problems with relatively "clean" non-domestic sewage inflow and infiltration, such as construction precipitation or foundation pit drainage, river and lake water backflow, and groundwater inflow and infiltration. The dilution and oxidation of low-concentration non-domestic sewage, i.e., inflowing clean water, on sewage is an important reason for the low influent concentration of sewage treatment plants and the treatment water volume far exceeding the sewage discharge volume, which seriously affects the normal performance of the sewage collection and treatment system. Clean water inflowing into the sewage pipe network will inevitably dilute the sewage pollutants. Taking effective methods and measures to investigate and diagnose the proportion of clean water in the sewage pipe network is an important means to improve the efficiency of sewage collection and treatment facilities, and can provide effective technical support for the subsequent clean water tracing and withdrawal work. At present, the characteristic water quality factor method based on chemical mass balance is widely used at home and abroad to quantitatively calculate the clean pollution ratio of urban sewage pipe networks. This method mainly relies on the results of pollutant concentration measurement for result measurement. To a certain extent, it overcomes the problems of inaccurate flow monitoring such as non-full pipe flow in sewage pipe networks. However, this method focuses on the chemical mass balance of pollutants affected by the dilution effect of influent clean water, and ignores the oxidation effect of the higher oxidation-reduction potential (ORP) of influent clean water on conventional pollutants in pipe network sewage. In actual application, problems such as incomplete output results and out-of-range measurement ratios often occur.

[0003] In general, the redox potential of domestic sewage in the sewage network is often between -400 and -200mV, which is reducing; the ORP of common inflow clean water such as urban river and lake water, groundwater, and rainwater is between 100 and 400mV, which is highly oxidizing. Clean water inflowing into the sewage network is mixed with domestic sewage, which has a certain oxidation effect on conventional pollutants in domestic sewage. The oxidation and degradation of these pollutants has not been reflected in previous calculation models, which has a certain impact on the accuracy of the calculation results. Therefore, the patent of this invention establishes a benchmark curve for the influence of clean water inflow on the oxidation attenuation of pollutants in the sewage network service area, and forms a calculation model that takes into account the oxidation effect of inflow clean water on pollutants and the attenuation effect of pollutants themselves, which can effectively improve the accuracy and practicality of the calculation results of the clean water ratio of the sewage network. Summary of the invention

[0004] The purpose of the present invention is to further improve the existing sewage network clean pollution ratio calculation model based on chemical mass balance, and propose a method for determining the oxidation attenuation ratio of inflowing clean water to conventional pollutants in sewage. Through this method, a baseline curve of the influence of clean water inflow on the oxidation attenuation of pollutants in the sewage network service area is established, and the oxidation effect of clean water's own oxidizing property on pollutants and the attenuation effect of pollutants themselves are quantified and incorporated into the calculation model based on chemical mass balance to improve the accuracy of the calculation results of the sewage network clean pollution ratio.

[0005] A method for calculating the clean sewage ratio of a sewage pipeline taking into account the oxidizability of the inflow clean water itself comprises the following steps:

[0006] Step S1. Sampling clean water sources with different ORPs in the sewage pipe network service area with inflow infiltration risks, and conducting mixing experiments with domestic sewage at ratios of 1:9, 1:4, 2:3 and 3:2, respectively, monitoring the ORP and characteristic pollutant concentration change trends of the mixed system, and establishing a baseline curve for the effect of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area;

[0007] Step S2. For the pipe section where clean water inflow actually occurs, define the upstream and downstream monitoring range of the clean water inflow point of the sewage pipe, select the inlet monitoring point k1 and the outlet monitoring point k2, and measure the inlet pollutant concentration C1 and the outlet pollutant concentration C2 respectively;

[0008] Step S3. Check the type and source of the incoming clean water, and measure the clean water ORP and pollutant concentration C3;

[0009] Step S4. Estimate the clean water ratio i of the sewage network using the chemical mass balance equation of pollutants at the inlet and outlet points of the sewage pipe;

[0010] Step S5. Determine the average flow velocity v of the pipeline between the inlet monitoring point k1 and the outlet monitoring point k2, and estimate the hydraulic retention time t of the sewage in the pipeline in combination with the pipeline length s between k1 and k2;

[0011] Step S6. According to the estimated clean water proportion i, the inflow clean water ORP and the hydraulic retention time t, the reference curve of the clean water inflow on the pollutant oxidation attenuation in the sewage pipe network service area obtained in step S1 is used to determine the characteristic pollutant attenuation ratio γ;

[0012] Step S7. Calculate the percentage of sewage pipe cleaning based on the data collected and measured in steps S1 to S6.

[0013] Furthermore, the clean water source in step S1 includes one or more of river water, lake water, groundwater and rainwater, and the ORP range of the clean water source is between 50 and 700 mV.

[0014] Furthermore, when performing the mixing experiment in step S1, the pipe network sludge is mixed with domestic sewage to simulate the microbial environment in the sewage pipe network, and an agitator is used to prevent the deposition of particles to simulate the flow state of sewage in the pipe network.

[0015] Furthermore, the establishment of a baseline curve for the effect of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area in step S1 is achieved by mixing the inflowing clean water with domestic sewage in different proportions, sampling the mixing system at different times, monitoring changes in SCOD concentration, and drawing a SCOD attenuation ratio change curve based on the clean water ratio, hydraulic retention time and clean water ORP.

[0016] The SCOD attenuation ratio calculation method is as follows:

[0017]

[0018] Furthermore, in step S2, the inlet and outlet pollutant concentrations refer to SCOD concentrations. During the detection, continuous sampling is performed during the peak period of residential water use, with a sampling frequency of not less than 4 times / hour and a sampling quantity of not less than 5. The inlet and outlet SCOD concentrations are taken as the inlet and outlet pollutant concentrations C1 and C2 using the arithmetic mean of the test result confidence interval [10%, 90%] data, in mg / L.

[0019] Furthermore, the clean water pollutant concentration in step S3 refers to the SCOD concentration. The number of samples taken during the detection is not less than 5, and the arithmetic mean of the SCOD concentrations of all samples is calculated as the inflow clean water pollutant concentration C3, in mg / L;

[0020] The number of samples for clean water ORP testing shall not be less than 10, and the arithmetic mean of all samples shall be calculated as the test result in mV.

[0021] Furthermore, the chemical mass balance equation of pollutants at the inlet and outlet points of the sewage pipe in step S4 refers to a method for calculating the proportion of clean water in the sewage pipe based on dilution balance, and the calculation formula is as follows:

[0022] C1Q1+C3Q3=C2Q2

[0023] Q1+Q3=Q2

[0024] Among them, Q1, Q2 and Q3 are the inlet flow, outlet flow and clean water inflow respectively. The following formula is used to estimate the clean water proportion i:

[0025]

[0026] Furthermore, the characteristic pollutant attenuation ratio γ in step S6 is a baseline curve of the influence of clean water inflow on pollutant oxidation attenuation in the sewage network service area established in step S1, and the corresponding SCOD concentration attenuation ratio is obtained according to the estimated three indicators of pipeline clean water ratio, hydraulic retention time and clean water ORP. The SCOD concentration attenuation ratio includes the natural attenuation of domestic sewage during the collection and transmission process and the oxidative degradation after mixing with clean water.

[0027] Furthermore, the calculation of the percentage of sewage pipe cleaning described in step S7 refers to a method for calculating the percentage of sewage pipe cleaning based on chemical mass balance, which takes into account the oxidative degradation effect of clean water itself on pollutants. The model is as follows:

[0028] C1Q1+C3Q3-γ(C1Q1+C3Q3)=C2Q2

[0029] Q1+Q3=Q2

[0030]

[0031] After simplification, the calculation formula for the clean pollution ratio is as follows:

[0032] Clean water ratio:

[0033] Sewage proportion:

[0034] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0035] (1) The present invention quantifies the effect of the oxidation of pollutants by the inflowing clean water on the dilution balance of pollutants in the pipeline, improves the existing sewage network clean pollution ratio calculation model based on chemical mass balance, and can effectively improve the accuracy and reliability of the calculation results of the sewage pipeline clean pollution ratio.

[0036] (2) The present invention proposes a method for determining the oxidation attenuation ratio of clean water inflow to conventional pollutants in sewage. This method is used to establish a baseline curve for the effect of clean water inflow on the oxidation attenuation of pollutants in the sewage network service area, providing technical support for cities and similar areas to efficiently and quickly calculate the proportion of clean water in the sewage pipe after clean water inflow.

[0037] (3) The present invention clarifies the specific steps of the sewage pipe clean pollution ratio calculation process. The method is simple and easy to operate. It has practical significance for scientifically guiding the diagnosis and evaluation of clean water inflow problems in sewage pipe networks and improving the operating efficiency of sewage collection and treatment facilities.

[0038] (4) At present, when calculating the percentage of sewage pipes cleaned after clean water flows into the urban drainage network, the main focus is on the role of dilution in reducing the concentration of pollutants, and the oxidation effect of the clean water itself on the pollutants in the sewage is ignored. In response to this loophole, the present invention proposes a method for determining the oxidation attenuation ratio of conventional pollutants in sewage by clean water, establishes a sewage pipe cleaned percentage calculation model and method considering the clean water itself, improves the accuracy of the sewage pipe cleaned percentage calculation results, and has practical significance for scientifically guiding the clean water withdrawal plan of the sewage network and improving the quality and efficiency of sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of a method for calculating the cleaning ratio of a sewage pipe taking into account the oxidizability of the inflowing clean water itself in an embodiment of the present invention.

[0040] Figure 2 It is the baseline curve of the effect of clean water inflow on the oxidation attenuation of pollutants when clean water and domestic sewage are mixed in a volume ratio of 3:2. DETAILED DESCRIPTION

[0041] A method for calculating the percentage of sewage pipe cleaning considering the oxidizability of the inflowing clean water, comprising the following steps:

[0042] Step S1. Sample clean water sources with different ORPs that have inflow infiltration risks in the sewage network service area, conduct mixing experiments with domestic sewage at volume ratios of 1:9, 1:4, 2:3 and 3:2, monitor the ORP and characteristic pollutant concentration change trends of the mixed system, and establish a baseline curve for the effect of clean water inflow on pollutant oxidation attenuation in the sewage network service area.

[0043] Clean water sources include one or more of urban river and lake water, groundwater and rainwater. The ORP range of clean water sources is between 50 and 700 mV. The higher the ORP value, the stronger the oxidizing property.

[0044] When conducting the mixing experiment, the pipe network sludge and domestic sewage were mixed in a volume ratio of 1:100 to simulate the microbial environment in the sewage pipe network, and an agitator was used to prevent the deposition of particulate matter and simulate the flow state of sewage in the pipe network.

[0045] The establishment of a baseline curve for the effect of clean water inflow on the oxidative attenuation of pollutants in the sewage network service area is achieved by mixing the inflowing clean water with domestic sewage in different proportions, sampling the mixing system at the moment of mixing and 2h, 4h, 6h and 8h after mixing, monitoring the changes in SCOD concentration, and drawing a SCOD attenuation ratio change curve based on the clean water ratio, hydraulic retention time and clean water ORP.

[0046] The SCOD attenuation ratio is calculated as follows:

[0047]

[0048] Where n = 2h, 4h, 6h and 8h.

[0049] Step S2. For the pipe section where clean water actually flows in, define the upstream and downstream monitoring range of the clean water inflow point of the sewage pipe, select the inlet monitoring point k1 and the outlet monitoring point k2, and measure the inlet pollutant concentration C1 and the outlet pollutant concentration C2 respectively.

[0050] The inlet and outlet pollutant concentrations refer to the SCOD concentrations. During the test, continuous sampling is carried out during the peak period of residential water use, with a sampling frequency of no less than 4 times / hour and a sampling quantity of no less than 5. The inlet and outlet SCOD concentrations are taken as the inlet and outlet pollutant concentrations C1 and C2 with the arithmetic mean of the test result confidence interval [10%, 90%] data, in mg / L.

[0051] When delineating the upstream and downstream monitoring range of the clean water inflow point of the sewage pipe, the clean water inflow point should be covered, and the pipe section with the fewest branch pipes should be intercepted as much as possible.

[0052] Step S3: Check the type and source of the incoming clean water, and measure the clean water ORP and pollutant concentration C3.

[0053] The clean water pollutant concentration refers to the SCOD concentration. The number of samples taken during the test shall not be less than 5. The arithmetic mean of the SCOD concentrations of all samples shall be calculated as the inflow clean water pollutant concentration C3, in mg / L.

[0054] The ORP of clean water is tested using a portable dual-channel water quality meter. The number of samples is not less than 10, and the arithmetic mean of all samples is calculated as the test result in mV.

[0055] Step S4. Estimate the clean water ratio i of the sewage network using the chemical mass balance equation of pollutants at the inlet and outlet points of the sewage pipe;

[0056] The chemical mass balance equation of pollutants at the inlet and outlet points of the sewage pipe refers to the calculation method of the clean water ratio of the sewage pipe based on the dilution balance. The calculation formula is as follows:

[0057] C1Q1+C3Q3=C2Q2

[0058] Q1+Q3=Q2

[0059] Among them, Q1, Q2 and Q3 are the inlet flow, outlet flow and clean water inflow respectively. The following formula is used to estimate the clean water proportion i:

[0060]

[0061] Step S5. Determine the average flow velocity v of the pipeline between the water inlet monitoring point k1 and the water outlet monitoring point k2, and estimate the hydraulic retention time t of the sewage in the pipeline in combination with the pipeline length s between k1 and k2.

[0062] The average flow velocity v of the pipeline is the average value of the flow velocities at multiple points within the monitoring range. The number of measuring points is no less than 5, and the flow velocity is continuously monitored using a Doppler flowmeter.

[0063] Step S6. According to the estimated clean water proportion i, the inflow clean water ORP and the hydraulic retention time t, the baseline curve of the clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area obtained in step S1 is used to determine the characteristic pollutant attenuation ratio γ.

[0064] The characteristic pollutant attenuation ratio γ is the baseline curve of the effect of clean water inflow on pollutant oxidation attenuation in the sewage network service area established in step S1. The corresponding SCOD concentration attenuation ratio is obtained based on the estimated three indicators: pipeline clean water ratio, hydraulic retention time and clean water ORP. The SCOD concentration attenuation ratio includes the natural attenuation of domestic sewage during collection and transmission and the oxidative degradation after mixing with clean water.

[0065] Step S7. Calculate the percentage of sewage pipe cleaning based on the data collected and measured in steps S1 to S6.

[0066] The calculation of the proportion of sewage pipe cleaning is a method of calculating the proportion of sewage pipe cleaning based on chemical mass balance, which takes into account the oxidative degradation of pollutants by the oxidative property of clean water itself. The model is as follows:

[0067] C1Q1+C3Q3-γ(C1Q1+C3Q3)=C2Q2

[0068] Q1+Q3=Q2

[0069]

[0070] After simplification, the calculation formula for the clean pollution ratio is as follows:

[0071] Clean water ratio:

[0072] Sewage proportion:

[0073] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0074] Example 1

[0075] like Figure 1As shown, a method for calculating the clean sewage ratio in a sewage pipeline considering the self-oxidizability of the incoming clean water includes the following steps:

[0076] Step S1. Calculate the clean-pollution ratio for a pipe section in the south that is greatly affected by the inflow of external clean water, sample clean water sources with different ORPs that have inflow and infiltration risks in the sewage pipe network service area, conduct mixing experiments with domestic sewage at ratios of 1:9, 1:4, 2:3 and 3:2, measure the change trends of ORP and characteristic pollutant concentrations, and establish a baseline curve for the influence of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area;

[0077] Step S2. For the pipe section where clean water actually flows in, the upstream and downstream monitoring ranges of the clean water inflow point of the sewage pipe are delineated, the main pipe with fewer converging branches upstream and downstream of the clean water inflow point of the pipeline is intercepted as the monitoring range, the inlet monitoring point k1 and the outlet monitoring point k2 are selected, and the inlet pollutant concentration C1 is measured to be 419 mg / L and the outlet pollutant concentration C2 is measured to be 185 mg / L respectively;

[0078] Step S3. Check the type and source of the incoming clean water, and make sure that the incoming clean water is urban landscape river and lake water. Use HACH 40d portable dual-channel water quality meter to detect that the ORP of river and lake water is 183mV and the clean water pollutant concentration C3 is 16.1mg / L;

[0079] When checking the type and source of the incoming clean water, the flow balance method, the minimum flow method at night, the triangle method, the minimum moving method, etc. can generally be used. The flow balance method is used in this embodiment.

[0080] Step S4. Using the chemical mass balance equation of pollutants at the sewage pipe inlet and outlet points: The clean water proportion i(%) of the sewage network was estimated to be 58.1%;

[0081] Step S5. The flow velocity of five points within the monitoring range was monitored using a Doppler flow meter, which were 0.047 m / s, 0.045 m / s, 0.043 m / s, 0.037 m / s and 0.064 m / s, respectively, with an average flow velocity of 0.047 m / s. The length of the main pipeline within the monitoring range was 1200 m, and the hydraulic retention time was determined to be 7 h.

[0082] Step S6. Based on the estimated clean water ratio i=58.1%, river and lake water ORP=183mV, and hydraulic retention time=7h, the baseline curve of the effect of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area (such as the attached Figure 2 The interpolation readings were used to obtain the attenuation ratio γ of the sewage SCOD concentration in 7 hours, which was 25.25%;

[0083] Step S7. Based on the data obtained in steps S1 to S6, the method for calculating the proportion of sewage pipe clean water based on chemical mass balance and considering the self-oxidizability of the inflow clean water proposed by the present invention is as follows:

[0084] Clean water ratio:

[0085] Sewage proportion:

[0086] It is calculated that clean water accounts for 42.6% and sewage accounts for 57.4%.

[0087] Example 2

[0088] like Figure 1 As shown, a method for calculating the clean sewage ratio in a sewage pipeline considering the self-oxidizability of the incoming clean water includes the following steps:

[0089] Step S1. Calculate the clean-pollution ratio for a pipe section in the south that is greatly affected by the inflow of external clean water, sample clean water sources with different ORPs that have inflow and infiltration risks in the sewage pipe network service area, conduct mixing experiments with domestic sewage at ratios of 1:9, 1:4, 2:3 and 3:2, measure the change trends of ORP and characteristic pollutant concentrations, and establish a baseline curve for the influence of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area;

[0090] Step S2. For the pipe section where clean water actually flows in, the upstream and downstream monitoring ranges of the clean water inflow point of the sewage pipe are delineated, the main pipe with fewer converging branches upstream and downstream of the clean water inflow point of the pipeline is intercepted as the monitoring range, the inlet monitoring point k1 and the outlet monitoring point k2 are selected, and the inlet pollutant concentration C1 and the outlet pollutant concentration C2 are measured to be 368 mg / L and 176 mg / L respectively;

[0091] Step S3. Check the type and source of the incoming clean water, confirm that the incoming clean water is rainwater, and use the HACH 40d portable dual-channel water quality meter to detect that the initial rainwater collected from the roof has an ORP of 214mV and a clean water pollutant concentration C3 of 30mg / L;

[0092] When checking the type and source of inflowing clean water, generally, the flow balance method, the minimum flow method at night, the triangle method, the minimum moving method, etc. can be used. The flow balance method is used in this embodiment.

[0093] Step S4. Using the chemical mass balance equation of pollutants at the sewage pipe inlet and outlet points: The clean water proportion i(%) of the sewage network was estimated to be 56.8%;

[0094] Step S5. The flow velocity of 5 points within the monitoring range was monitored using a Doppler flow meter, which were 0.110 m / s, 0.114 m / s, 0.089 m / s, 0.094 m / s and 0.103 m / s, respectively, with an average flow velocity of 0.102 m / s; the length of the main pipeline within the monitoring range was 1500 m, and the hydraulic retention time was determined to be 4 h;

[0095] Step S6. Based on the estimated clean water ratio i=56.8%, rainwater ORP=214mV, hydraulic retention time=4h, the baseline curve of the effect of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area (such as the attached Figure 2 The attenuation ratio γ of the sewage SCOD concentration in 4 hours is 6%.

[0096] Step S7. Based on the data obtained in steps S1 to S6, the method for calculating the proportion of sewage pipe clean water based on chemical mass balance and considering the self-oxidizability of the inflow clean water proposed by the present invention is as follows:

[0097] Clean water ratio:

[0098] Sewage proportion:

[0099] It is calculated that clean water accounts for 53.5% and sewage accounts for 46.5%.

[0100] Example 3

[0101] like Figure 1 As shown, a method for calculating the clean sewage ratio in a sewage pipeline considering the self-oxidizability of the incoming clean water includes the following steps:

[0102] Step S1. Calculate the clean-pollution ratio for a pipe section in the south that is greatly affected by the inflow of external clean water, sample clean water sources with different ORPs that have inflow and infiltration risks in the sewage pipe network service area, conduct mixing experiments with domestic sewage at ratios of 1:9, 1:4, 2:3 and 3:2, measure the change trends of ORP and characteristic pollutant concentrations, and establish a baseline curve for the influence of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area;

[0103] Step S2. For the pipe section where clean water actually flows in, the upstream and downstream monitoring ranges of the clean water inflow point of the sewage pipe are delineated, the main pipe with fewer converging branches upstream and downstream of the clean water inflow point of the pipeline is intercepted as the monitoring range, the inlet monitoring point k1 and the outlet monitoring point k2 are selected, and the inlet pollutant concentration C1 and the outlet pollutant concentration C2 are measured to be 348 mg / L and 152 mg / L respectively;

[0104] Step S3. Check the type and source of the incoming clean water, make sure that the incoming clean water is river or lake water, use HACH 40d portable dual-channel water quality meter to detect that the ORP of river and lake water is 149mV, and the clean water pollutant concentration C3 is 29.8mg / L;

[0105] When checking the type and source of inflowing clean water, generally, the flow balance method, the minimum flow method at night, the triangle method, the minimum moving method, etc. can be used. The flow balance method is used in this embodiment.

[0106] Step S4. Using the chemical mass balance equation of pollutants at the sewage pipe inlet and outlet points: The clean water proportion i(%) of the sewage network was estimated to be 61.6%;

[0107] Step S5. The flow velocity of 5 points within the monitoring range was monitored using a Doppler flow meter, which were 0.045 m / s, 0.042 m / s, 0.038 m / s, 0.039 m / s, and 0.047 m / s, respectively, with an average flow velocity of 0.042 m / s; the length of the main pipeline within the monitoring range was 500 m, and the hydraulic retention time was determined to be 3 h;

[0108] Step S6. Based on the estimated clean water proportion i=61.6%, river and lake water ORP=149mV, and hydraulic retention time=3h, the baseline curve of the effect of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area (such as the attached Figure 2 The interpolation readings were used to obtain the attenuation ratio γ of the sewage SCOD concentration in 3 hours, which was 0.5%;

[0109] Step S7. Based on the data obtained in steps S1 to S6, the method for calculating the proportion of sewage pipe clean water based on chemical mass balance and considering the self-oxidizability of the inflow clean water proposed by the present invention is as follows:

[0110] Clean water ratio:

[0111] Sewage proportion:

[0112] It is calculated that clean water accounts for 61.4% and sewage accounts for 38.6%.

[0113] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for calculating the proportion of sewage pipe cleaning by considering the self-oxidizing property of the inflowing clean water, characterized in that: The following steps are involved: Step S1. Sampling clean water sources with different ORPs in the sewage pipe network service area with inflow infiltration risks, and conducting mixing experiments with domestic sewage at different volume ratios, monitoring the ORP and characteristic pollutant concentration change trends of the mixed system, and establishing a baseline curve for the effect of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area; Step S2. For the pipe section where clean water inflow actually occurs, define the upstream and downstream monitoring range of the clean water inflow point of the sewage pipe, select the inlet monitoring point k1 and the outlet monitoring point k2, and measure the inlet pollutant concentration C1 and the outlet pollutant concentration C2 respectively; Step S3. Check the type and source of the incoming clean water, and measure the clean water ORP and pollutant concentration C3; Step S4. Estimate the clean water ratio i of the sewage network using the chemical mass balance equation of pollutants at the sewage pipe inlet and outlet points; Step S5. Determine the average flow velocity v of the pipeline between the inlet monitoring point k1 and the outlet monitoring point k2, and estimate the hydraulic retention time t of the sewage in the pipeline in combination with the pipeline length s between k1 and k2; Step S6. According to the estimated clean water proportion i, the inflow clean water ORP and the hydraulic retention time t, the reference curve of the clean water inflow on the pollutant oxidation attenuation in the sewage pipe network service area obtained in step S1 is used to determine the characteristic pollutant attenuation ratio γ; Step S7. Calculate the percentage of sewage pipe cleaning based on the data collected and measured in steps S1 to S6; The calculation of the percentage of sewage pipe cleaning described in step S7 refers to a method for calculating the percentage of sewage pipe cleaning based on chemical mass balance, which takes into account the oxidative degradation effect of clean water itself on pollutants. The model is as follows: ， After simplification, the calculation formula for the clean pollution ratio is as follows: ； Among them, Q1, Q2 and Q3 are the inlet flow, outlet flow and clean water inflow respectively.

2. The method for calculating the proportion of sewage pipe cleaning according to claim 1, wherein the method is characterized in that: The clean water source in step S1 includes one or more of river water, lake water, groundwater and rainwater, and the ORP range of the clean water source is between 50 and 700 mV.

3. The method for calculating the proportion of sewage pipe cleaning according to claim 1, wherein the method is characterized in that: When performing the mixing experiment in step S1, the pipe network sludge is mixed with domestic sewage to simulate the microbial environment in the sewage pipe network, and an agitator is used to stir to prevent particle deposition and simulate the flow state of sewage in the pipe network.

4. The method for calculating the proportion of sewage pipe cleaning according to claim 1, wherein the method is characterized in that: The establishment of the baseline curve of the effect of clean water inflow on pollutant oxidation attenuation in the sewage pipe network service area in step S1 is achieved by mixing the inflow clean water with domestic sewage in different proportions, sampling the mixing system at different times, monitoring the change in SCOD concentration, and drawing a SCOD concentration attenuation ratio change curve based on the clean water ratio, hydraulic retention time and clean water ORP.

5. The method for calculating the percentage of sewage pipe cleaning considering the self-oxidizability of inflow clean water according to claim 1 is characterized in that: The inlet and outlet pollutant concentrations in step S2 refer to SCOD concentrations. During the detection, continuous sampling is performed during the peak period of residential water use, with a sampling frequency of no less than 4 times / hour and a sampling quantity of no less than 5. The inlet and outlet SCOD concentrations are taken as the inlet and outlet pollutant concentrations C1 and C2 with the arithmetic mean of the test result confidence interval [10%, 90%] data, in mg / L.

6. The method for calculating the percentage of sewage pipe cleaning according to claim 1, wherein the method is characterized in that: The clean water pollutant concentration in step S3 refers to the SCOD concentration. The number of samples taken during the detection is not less than 5. The arithmetic mean of the SCOD concentrations of all samples is calculated as the inflow clean water pollutant concentration C3, in mg / L; The number of samples for clean water ORP testing shall not be less than 10, and the arithmetic mean of all samples shall be calculated as the test result in mV.

7. The method for calculating the percentage of sewage pipe cleaning considering the self-oxidizability of inflow clean water according to claim 1, characterized in that: The chemical mass balance equation of pollutants at the inlet and outlet points of the sewage pipe in step S4 refers to a method for calculating the proportion of clean water in the sewage pipe based on dilution balance, and the calculation formula is as follows: ， The following formula is used to estimate the clean water ratio i: 。 8. The method for calculating the percentage of sewage pipe cleaning according to claim 1, wherein the method is characterized in that: The characteristic pollutant attenuation ratio γ in step S6 is a baseline curve of the influence of clean water inflow on pollutant oxidation attenuation in the sewage network service area established in step S1. The corresponding SCOD concentration attenuation ratio is obtained according to the estimated three indicators: proportion of pipeline clean water, hydraulic retention time and clean water ORP. The SCOD concentration attenuation ratio includes the natural attenuation of domestic sewage during collection and transmission and the oxidative degradation after mixing with clean water.

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