Method and system for calculating residual chlorine distribution in a clear water tank

Abstract

The present application relates to a method and system for calculating the distribution of residual chlorine in a clear water tank, and belongs to the field of drinking water chlorination disinfection technology. First, a residual chlorine decay curve of the water sample is fitted, and then the clear water tank is grid processed using fluid mechanics simulation software to establish a clear water tank inflow and outflow prediction model. The inflow and outflow of the clear water tank in a certain period of time is predicted using the clear water tank inflow and outflow prediction model, and the flow distribution of each grid inside the clear water tank is simulated using fluid mechanics simulation software. The hydraulic retention time of each grid unit and the total cumulative hydraulic retention time from the inlet of the clear water tank to each grid unit along the horizontal direction of the water flow are calculated, the residual chlorine concentration of the chlorinated raw water passing through each grid of the clear water tank is calculated through the residual chlorine decay curve, and the residual chlorine concentration of each grid unit is updated in real time by setting a time step. The present application can accurately predict and manage the residual chlorine distribution from the inlet to the outlet of the clear water tank, thereby ensuring water quality safety and providing a basis for improving the efficiency of disinfectant use.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and system for calculating the distribution of residual chlorine in a clear water tank, belonging to the field of drinking water chlorination disinfection technology. BACKGROUND

[0002] Residual chlorine is a key chemical substance used to ensure water quality safety in water supply systems, but it gradually decays during storage and transportation. The clear water tank is an important part of the water treatment system, which stores and treats treated clear water to ensure that the water quality meets the standards. After chlorination of filtered water, the water passes through the water delivery pipe and the clear water tank in sequence, with the longest time in the clear water tank and greater consumption of residual chlorine. Therefore, the calculation and prediction of residual chlorine decay in the clear water tank are particularly important.

[0003] Traditional residual chlorine decay calculation methods often use empirical values for estimation, but their accuracy and applicability are limited under complex hydraulic conditions. This method ignores the spatial variability of water flow, mixing, and reaction processes in the clear water tank, as well as the changes in water inflow and outflow at different times. This leads to deviations between the calculated results and the actual situation, making it difficult to accurately guide water quality management and residual chlorine control. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned deficiencies and provide a method for calculating the distribution of residual chlorine in a clear water tank, which takes into account the spatial distribution and flow characteristics of water flow in the tank, and can simulate the residual chlorine decay process in each grid cell in detail, thereby improving the accuracy of residual chlorine decay prediction.

[0005] The technical solution adopted by the present application is as follows:

[0006] A method for calculating the distribution of residual chlorine in a clear water tank, comprising the following steps:

[0007] S1. Take a water sample near the inlet of the clear water tank, record the residual chlorine concentration at different time points, and use the parallel first-order reaction model of residual chlorine to fit the data to obtain the residual chlorine decay curve of the water sample;

[0008] S2. Use fluid mechanics simulation software to grid the clear water tank according to its geometry and internal structure, divide it into multiple cubic grid cells, and record the position of each grid cell;

[0009] S3. According to the historical data of the change of water inflow and outflow of the clear water tank with time, use a conventional deep learning algorithm to train a model to establish a clear water tank inflow and outflow prediction model;

[0010] S4. Use the water inflow and outflow prediction model of the clear water tank to predict the water inflow and outflow of the clear water tank within a certain period of time. Based on the geometry, internal structure, grid size, and water inflow and outflow of the clear water tank, use fluid dynamics simulation software to simulate the flow distribution of each grid inside the clear water tank.

[0011] S5. Calculate the hydraulic residence time (HRT) for each grid cell. x The total cumulative hydraulic residence time (HRT) from the inlet of the clear water tank along the horizontal direction of the water flow to each grid cell. n总 Hydraulic Retention Time (HRT) of each grid cell x for:

[0012]

[0013] Where V is the volume of each grid cell, Q x It is the flow through this grid cell;

[0014] S6. The total cumulative hydraulic retention time (HRT) from the clear water tank inlet to each grid unit. n总 Substituting the residual chlorine decay curve from step S1, the residual chlorine concentration of the chlorinated raw water passing through each grid of the clear water tank is calculated using the residual chlorine decay curve. Based on the real-time monitored residual chlorine level C0 at the inlet of the clear water tank, the residual chlorine concentration C in each grid section of the clear water tank and the residual chlorine concentration C at the outlet of the clear water tank are then derived. 出 ;

[0015] S7. Set the time step Δt, and update the residual chlorine concentration of each grid unit in real time according to the inflow and outflow of the clear water tank within the time Δt, so as to predict the decay and residual chlorine distribution in the clear water tank.

[0016] In the above method, the parallel first-order reaction model formula for residual chlorine used in step S1 is as follows:

[0017]

[0018] In the formula, t represents the reaction time, x represents the percentage of the initial residual chlorine concentration participating in the fast reaction relative to the total initial residual chlorine concentration, C0 is the total initial residual chlorine concentration, and k f k is the decay constant of the fast reaction of residual chlorine. s Where C is the residual chlorine slow reaction decay constant, and C is the residual chlorine concentration;

[0019] The initial residual chlorine concentration participating in the rapid reaction is the residual chlorine concentration participating in the reaction within 0-30 min, where x is the initial residual chlorine concentration minus the ratio of the residual chlorine concentration sampled at 30 min to the initial residual chlorine concentration. The calculation formula is as follows:

[0020] x=y(C0-C 30 ) / C0,

[0021] In the formula, Co is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration at 30 minutes, and y is an adjustment coefficient, which is 1.15.

[0022] The least square method is used to fit k f and k s , and k s and k f are obtained, so that the function relationship of the residual chlorine concentration C with respect to time t can be obtained.

[0023] The fluid mechanics simulation software in step S2 includes but is not limited to FLOW-3D model software and CFX model software, can support complex geometric modeling and mesh division, and can accurately simulate the flow distribution inside the clear water tank.

[0024] The HRT n总 in step S5 is the sum of the hydraulic retention time of all grid units in the horizontal direction of the water flow from the entrance of the clear water tank to the nth grid unit. Therefore, the HRT n总 includes the single hydraulic retention time HRT x of all grid units in the horizontal direction of the water flow path in the horizontal direction of the water flow path, x = 1, 2, 3…n, and the formula is as follows:

[0025] HRT n总 = HRT1 + HRT2 + … + HRT(n-1) + HRTx.

[0026] Another object of the present application is to provide a clear water tank residual chlorine distribution calculation system, which comprises a residual chlorine decay curve model construction module, which uses the residual chlorine concentration of the water sample at different time points in the clear water tank near the water inlet and the parallel first-order reaction model of the residual chlorine to fit the data and obtain the residual chlorine decay curve of the water sample;

[0027] A fluid mechanics simulation software processing module uses fluid mechanics simulation software to grid process the clear water tank according to the geometric shape and internal structure of the clear water tank, divide the clear water tank into multiple cubic grid units, record the position of each grid unit, and simulate the flow distribution of each grid inside the clear water tank according to the geometric shape and internal structure of the clear water tank, the grid size, and the water inflow and outflow;

[0028] A clear water tank water inflow and outflow prediction model module uses conventional deep learning algorithms to train a model and establish a clear water tank water inflow and outflow prediction model according to historical data of changes in the water inflow and outflow of the clear water tank with time, and uses the clear water tank water inflow and outflow prediction model to predict the water inflow and outflow of the clear water tank in a certain period;

[0029] A hydraulic retention time calculation module is used to calculate the hydraulic retention time of each grid unit and the total cumulative hydraulic retention time HRTn总 Hydraulic Retention Time (HRT) of each grid cell x for:

[0030]

[0031] Where V is the volume of each grid cell, Q x It is the flow through this grid cell.

[0032] HRT n总 It includes the single hydraulic residence time (HRT) of all grid cells in the horizontal flow path direction. x x = 1, 2, 3…n, the formula is as follows:

[0033] HRT n总 =HRT1+HRT2+...+HRT(n-1)+HRTx;

[0034] The residual chlorine concentration calculation module calculates the total cumulative hydraulic retention time (HRT) of each grid cell. n总 Substitute the residual chlorine decay curve into the residual chlorine decay curve to calculate the residual chlorine concentration of the chlorinated raw water passing through each grid of the clear water tank. Based on the real-time monitoring of the residual chlorine amount at the inlet of the clear water tank, the residual chlorine concentration of each grid in the clear water tank and the residual chlorine concentration at the outlet of the clear water tank are then obtained.

[0035] The residual chlorine concentration distribution display module is used to display the results of residual chlorine concentration distribution.

[0036] The residual chlorine calculation and update module is used to update the residual chlorine concentration of each grid unit in real time based on the inflow and outflow of the clear water tank within a set time step.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) By dividing the clear water tank into fine areas through grid modeling, combined with real-time residual chlorine data, the residual chlorine decay curve is used to predict the residual chlorine change trend, and the inlet and outlet water volume of the clear water tank is integrated to achieve accurate prediction and management of the residual chlorine distribution from the inlet to the outlet of the clear water tank, thereby ensuring water quality safety and providing a basis for improving the efficiency of disinfectant use.

[0039] (2) By gridding, the clear water tank is divided into multiple independent grid units. Each unit is calculated and simulated independently, which can simulate the decay process of residual chlorine in each grid unit in detail, thereby improving the accuracy of residual chlorine decay prediction.

[0040] (3) Through the grid modeling and real-time monitoring technology, the distribution of residual chlorine in the clear water tank is predicted, the monitoring efficiency and accuracy are improved, so that the chlorine dosage can be automatically adjusted according to the prediction result, the precise control of water quality safety is realized, compared with the traditional chlorine adding mode, the waste of chemicals is reduced, which is helpful to reduce the use amount of disinfectant, thereby reducing the operation cost, achieving the effect of energy saving and environmental protection. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 Flow chart of the calculation method of the present application. DETAILED DESCRIPTION

[0042] The present application will be described in detail below in combination with the drawings and examples.

[0043] Example 1 A calculation method of residual chlorine distribution in a clear water tank, as shown in Figure 1 , comprising the following steps:

[0044] S1. Take the water sample near the water inlet of the clear water tank, record the residual chlorine concentration at different time points, and use the parallel first-order reaction model of residual chlorine to fit the data to obtain the residual chlorine decay curve of the water sample:

[0045] (1) Take the water sample near the water inlet of the clear water tank, add the water sample into a brown container, and place the brown container in a constant temperature oven, and control the temperature to be constant at 13-19℃.

[0046] The purpose of controlling the temperature unchanged is to ensure that the residual chlorine decay can be carried out at the same temperature, and the measurement data is not affected by the change of temperature.

[0047] Take the above water sample, and measure the residual chlorine concentration C (mg / L) at different times, which means at 10 min, 20 min, 30 min, 60 min, 90 min, 120 min, 150 min, 180 min, 240 min, and use the following formula of parallel first-order reaction model to fit the data:

[0048]

[0049] In the formula, t represents the reaction time, x represents the percentage of the initial residual chlorine concentration participating in the fast reaction to the total initial residual chlorine concentration, C0 is the total initial residual chlorine concentration, k f is the fast reaction decay constant of residual chlorine, k s is the slow reaction decay constant of residual chlorine, and C is the residual chlorine concentration.

[0050] The residual chlorine decay contains two types of reactions in poor water quality, one is fast reaction, which is generally completed within 0.5 hours, and consumes 30%-60% of the residual chlorine, and the fast reaction decay constant of residual chlorine k fCorresponding to this process; another type is slow reaction, generally need 10-20 hours to complete, said the remaining chlorine slow reaction decay constant k s Corresponding to this process.

[0051] The least squares method is used to fit k f And k s Two parameters, k s And k f , the function of the residual chlorine concentration C about time t can be obtained.

[0052] The initial residual chlorine concentration participating in the fast reaction is the residual chlorine concentration participating in the reaction within 0-30 min. x is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 min to the initial residual chlorine concentration, and the calculation formula is as follows:

[0053] x=y(C0-C 30 ) / C0,

[0054] In the formula, C0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration at 30 min, and y is an adjustment coefficient, which is 1.15.

[0055] The residual chlorine is the sum of the concentrations of Cl2, HClO and ClO - .

[0056] S2. The fluid mechanics simulation software is used to grid the clear water tank according to the geometric shape and internal structure of the clear water tank, divide it into multiple cubic grid units, and record the position of each grid unit:

[0057] The volume of the grid unit is:

[0058] V=Δx*Δy*Δz,

[0059] Wherein: Δx, Δy, Δz are the sizes (length, width and height) of the grid in x, y and z directions.

[0060] S3. According to the historical data of the change of the inflow and outflow of the clear water tank with time, a model training is carried out by using a conventional deep learning algorithm to establish a clear water tank inflow and outflow prediction model:

[0061] The inflow and outflow data of the clear water tank in each time period (such as every hour) within one year are obtained, the missing values in the data are checked, and the missing data points are selected to be filled (such as using average value, median, previous value, etc.) or deleted according to the situation. The data set is divided into training set and test set (used to evaluate the performance of the model). After establishing the model by using the method of regression analysis, the performance of the model is evaluated by using the test set data. The error between the predicted value and the actual value is calculated, and continuous rating and correction are carried out to strive to achieve high prediction accuracy.

[0062] Finally, the inflow and outflow of the clear water tank at each time step can be obtained.

[0063] Preferably, the time period of the calculation time step is 10 min.

[0064] S4. Predict the inflow and outflow of the clear water tank in a certain period of time using the clear water tank inflow and outflow prediction model, and simulate the flow distribution of each grid in the clear water tank according to the geometric shape, internal structure, grid size, inflow and outflow of the clear water tank using fluid mechanics simulation software.

[0065] S5. Calculate the hydraulic retention time HRT of each grid unit x and the total cumulative hydraulic retention time HRT from the inlet of the clear water tank to each grid unit along the horizontal direction of the water flow n总 The hydraulic retention time HRT of each grid unit x is:

[0066]

[0067] where V is the volume of each grid unit, Q x is the flow through the grid unit.

[0068] The HRT n总 is the sum of the hydraulic retention time of all grid units in the horizontal direction of the water flow from the inlet of the clear water tank to the nth grid unit. Therefore, HRT n总 contains the single hydraulic retention time HRT x of all grid units in the horizontal direction of the water flow in the horizontal direction of the water flow, x = 1, 2, 3…n, and the formula is as follows:

[0069] HRT n总 = HRT1+ HRT2+…+ HRT(n-1)+ HRTx.

[0070] S6. Substitute the cumulative total hydraulic retention time from the inlet of the clear water tank to each grid unit into the residual chlorine decay curve of step S1, and calculate the residual chlorine concentration of the chlorinated raw water through each grid of the clear water tank by the residual chlorine decay curve, based on the real-time monitored residual chlorine amount C0 at the inlet of the clear water tank, to further obtain the residual chlorine concentration C of each grid part in the clear water tank and the residual chlorine concentration C 出 at the outlet of the clear water tank, and the calculation process is as follows:

[0071] (1) Calculate the total hydraulic retention time HRT n总 of each grid unit.

[0072] (2) Substitute the total hydraulic retention time HRT n总The residual chlorine decay curve of step S1 is substituted to obtain the residual chlorine amount C in each grid unit based on the residual chlorine amount C0 of the water inlet of the water tank.

[0073] S7. Set a time step Δt, and update the residual chlorine concentration of each grid unit in real time according to the water inflow and outflow of the water tank within the time Δt, and further predict the decay and residual chlorine distribution in the water tank:

[0074] In each time step Δt, the residual chlorine concentration in each grid unit is updated: preferably, the time step Δt is 10 min.

[0075] For each grid, the residual chlorine concentration of each grid at any time is calculated according to the residual chlorine decay model and the water flow, geometric parameters and initial residual chlorine concentration in the grid.

[0076] The residual chlorine concentration in each grid and the residual chlorine transmission between grids are preferably summarized, and the calculation results are output as a residual chlorine concentration distribution map to obtain a residual chlorine concentration distribution map of the entire water tank, which intuitively displays the distribution of the residual chlorine concentration in the water tank.

[0077] Embodiment 2: A residual chlorine distribution calculation system for a water tank, which can implement the method described in embodiment 1, comprising a residual chlorine decay curve model construction module, which uses the residual chlorine concentration of water samples at different time points and a parallel first-order reaction model of residual chlorine to fit the data and obtain the residual chlorine decay curve of the water samples;

[0078] A fluid mechanics simulation software processing module, which uses fluid mechanics simulation software to grid process the water tank according to the geometric shape and internal structure of the water tank, divide it into multiple cubic grid units, record the position of each grid unit, and simulate the flow distribution of each grid in the water tank according to the geometric shape, internal structure, grid size, and inflow and outflow of the water tank;

[0079] A water tank inflow and outflow prediction model module, which uses conventional deep learning algorithms to train a model and establish a water tank inflow and outflow prediction model according to historical data of the change of water inflow and outflow with time, and uses the water tank inflow and outflow to predict the inflow and outflow of the water tank in a certain period;

[0080] A hydraulic retention time calculation module for calculating the hydraulic retention time of each grid unit and the total cumulative hydraulic retention time HRT of each grid unit from the inlet of the water tank along the horizontal direction of the water flow. n总 The hydraulic retention time HRT of each grid unit is: x

[0081]

[0082] Wherein, V is the volume of each grid unit, Q x ​is the flow through the grid cell;

[0083] HRT n总 HRT of all grid cells in the direction of the horizontal water flow path x x = 1, 2, 3…n, and the formula is as follows:

[0084] HRT n总 = HRT1+ HRT2+…+ HRT(n-1)+ HRTx.

[0085] The residual chlorine concentration calculation module substitutes the cumulative total hydraulic retention time of each grid cell into the residual chlorine decay curve, calculates the residual chlorine concentration of each grid of the chlorinated raw water passing through the clear water pool through the residual chlorine decay curve, and obtains the residual chlorine concentration of each grid part of the clear water pool and the residual chlorine concentration of the outlet of the clear water pool based on the real-time monitored residual chlorine amount of the inlet of the clear water pool.

[0086] The residual chlorine concentration distribution display module is used for displaying the residual chlorine concentration distribution result.

[0087] The residual chlorine calculation updating module is used for calculating the inflow and outflow of the clear water pool according to the set time step, and updating the calculation of the residual chlorine concentration of each grid cell in real time.

[0088] The above merely describes specific embodiments of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for calculating the distribution of residual chlorine in a clearwell, characterized by, The steps include the following: S1. Take the water sample near the water inlet in the clear water tank, record the residual chlorine concentration at different time points, and use the parallel first-order reaction model of residual chlorine to fit the data to obtain the residual chlorine decay curve of the water sample; S2. The fluid mechanics simulation software is used to grid the clear water tank according to its geometric shape and internal structure, divide it into multiple cubic grid units, and record the position of each grid unit; S3. According to the historical data of the change of the inflow and outflow of the clear water tank with time, a model training is conducted using a conventional deep learning algorithm to establish a clear water tank inflow and outflow prediction model; S4. The clear water tank inflow and outflow prediction model is used to predict the inflow and outflow of the clear water tank in a certain period of time, and the flow distribution of each grid in the clear water tank is simulated according to the geometric shape, internal structure, grid size, and inflow and outflow of the clear water tank using the fluid mechanics simulation software; S5. Calculate the hydraulic residence time for each grid cell HRT x and the total cumulative hydraulic residence time from the clearwell inlet along the horizontal direction of the water flow to each grid cell HRT n总 the hydraulic residence time for each grid cell HRT x is: ， wherein, V is the volume of each grid cell, Q x is the flow through the grid cell; S6. Total cumulative hydraulic retention time of clear water pool inlet to each grid cell HRT n总 Substitute the residual chlorine decay curve of step S1, calculate the residual chlorine concentration of each grid of the chlorinated raw water passing through the clear water pool by the residual chlorine decay curve, and monitor the residual chlorine amount at the clear water pool inlet in real time C 0 As a basis, the residual chlorine concentration of each grid part in the clear water pool is further derived C and the residual chlorine concentration at the outlet of the clear water pool C 出 ; S7. Set the time step Δt, and according to the inflow and outflow of the clear water tank in the time Δt, the residual chlorine concentration of each grid unit is updated in real time, and then the decay and residual chlorine distribution in the clear water tank are predicted.

2. The method of claim 1, wherein the method is characterized by: The parallel first-order reaction model formula used in step S1 is as follows: ， wherein t represents the reaction time, x represents the percentage of the initial residual chlorine concentration involved in the fast reaction to the total initial residual chlorine concentration, C 0 is the total initial residual chlorine concentration, k f is the residual chlorine fast reaction decay constant, k s is the residual chlorine slow reaction decay constant, C is the residual chlorine concentration; The initial residual chlorine concentration participating in the fast reaction is the residual chlorine concentration participating in the reaction within 0-30 min, x is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 min to the total initial residual chlorine concentration, and the calculation formula is as follows: x = y C 0 - C 30 / C 0 wherein C 0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration at 30 minutes, and y is an adjustment factor of 1.

15. Fitting using the least squares method k f and k s Two parameters, to obtain k s and k f The residual chlorine concentration can then be obtained. C The functional relationship with respect to time t.

3. The method of claim 1, wherein the method is characterized by: The fluid mechanics simulation software in step S2 includes FLOW-3D model software and CFX model software.

4. The method according to claim 1, wherein the method is characterized by, Said in step S5 HRT n总 is the sum of the one-way hydraulic retention time of all grid cells from the inlet of the clear water pool to the nth grid cell in the horizontal direction of the water flow, HRT n总 contains the single hydraulic retention time of all grid cells in the horizontal water flow path direction in the horizontal water flow path direction HRT x , x=1,2,3…n, the formula is as follows: HRT n总 = HRT 1 + HRT 2 + ... + HRT (n-1) + HRT x 。 5. A system for calculating the distribution of residual chlorine in a clearwell, comprising: The residual chlorine decay curve model construction module is used to obtain the residual chlorine decay curve of the water sample by fitting the data of the residual chlorine concentration at different time points of the water sample near the water inlet in the clear water tank and the parallel first-order reaction model of residual chlorine; The fluid mechanics simulation software processing module is used to grid the clear water tank according to its geometric shape and internal structure, divide it into multiple cubic grid units, record the position of each grid unit, and simulate the flow distribution of each grid in the clear water tank according to the geometric shape, internal structure, grid size, and inflow and outflow of the clear water tank; The clear water tank inflow and outflow prediction model module is used to establish a clear water tank inflow and outflow prediction model according to the historical data of the change of the inflow and outflow of the clear water tank with time, and to predict the inflow and outflow of the clear water tank in a certain period of time using the clear water tank inflow and outflow prediction model; a hydraulic retention time calculation module for calculating the hydraulic retention time of each grid cell and the total cumulative hydraulic retention time from the clear water tank inlet to each grid cell HRT n总 the hydraulic retention time of each grid cell HRT x is: ， wherein, V is the volume of each grid cell, Q x is the flow through the grid cell, HRT n总 Single hydraulic residence time of all grid cells in the horizontal water flow path direction including the previous horizontal water flow path direction HRT x , x = 1, 2, 3...n, as follows: HRT n总 = HRT 1 + HRT 2 + ... + HR T(n-1) + HRT x ； a residual chlorine concentration calculation module, which calculates the total cumulative hydraulic retention time of each grid unit HRT n总 The residual chlorine concentration of each grid of the chlorinated raw water passing through the clear water pool is calculated through the residual chlorine decay curve, and the residual chlorine concentration of each grid part in the clear water pool and the residual chlorine concentration of the outlet of the clear water pool are obtained based on the residual chlorine amount of the inlet of the clear water pool monitored in real time. The residual chlorine concentration distribution display module is used to display the residual chlorine concentration distribution results. The residual chlorine calculation updating module is used to update the residual chlorine concentration of each grid unit in real time according to the inflow and outflow of the clear water tank in the set time step.

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