Method for calculating, regulating and controlling chlorine addition amount of waterworks

Abstract

The invention relates to a method for calculating, regulating and controlling the chlorine addition amount of a waterworks, and belongs to the technical field of water treatment. Firstly, a mathematical model of chlorine demand under different water quality parameters is established according to regression analysis of mass data obtained by a beaker experiment; fitting a residual chlorine attenuation curve; calculating the hydraulic retention time of the water body in the clean water tank and the hydraulic retention time T required by the raw water after chlorination to the outlet of the water plant; calculating the residual chlorine consumption of the raw water in the hydraulic retention time T by using the obtained residual chlorine attenuation curve; calculating the chlorine demand according to a mathematical model of the chlorine demand obtained according to the current water quality index; the chlorination amount is calculated through a chlorination amount calculation formula; and the residual chlorine in factory water is detected in real time, early warning is carried out in time when abnormity occurs, and the chlorine adding amount is adjusted in real time. The chlorine adding amount can be accurately calculated, meanwhile, the chlorine adding amount can be adjusted in real time according to the water quality change, the hydraulic retention time of the clean water tank and the residual chlorine content condition, the operation cost can be reduced, and the energy-saving and environment-friendly effects are achieved.

Description

Technical Field

[0001] The invention relates to a method for calculating and regulating the amount of chlorine added in a water plant, and belongs to the technical field of water treatment. Background Art

[0002] In the traditional tap water treatment process, chlorination disinfection is one of the key steps to ensure water quality safety. However, the existing chlorination control methods mostly rely on manual experience or fixed preset values, and it is difficult to adjust the chlorination amount in real time according to the changes in the raw water quality. This may cause a waste of disinfectants, and may affect the disinfection effect due to insufficient chlorination, and even cause the water quality to fail to meet the standards. Therefore, it is particularly important to develop an intelligent control method that can automatically adjust the chlorination amount according to changes in water quality.

[0003] At present, the chlorination process in the water treatment process is usually controlled by manual control or PLC system. However, due to the hysteresis characteristics of the chlorination system, its transition process and pure lag time are both long, and there are many interference factors in the system, which makes the adjustment more frequent and the control accuracy is poor, which leads to poor chlorination disinfection effect in the water treatment process. Patent CN115196730A discloses a sodium hypochlorite intelligent dosing system for water plants. Through the intelligent control of the integral differential control model, it can dynamically adjust the amount of post-chlorination according to the effect of pre-chlorination, and dynamically adjust the amount of supplementary chlorine according to the effect of pre-chlorination and post-chlorination. The system uses the chlorine supplementation control module at the outlet of the water plant clear water tank for adjustment. It is impossible to accurately calculate the amount of chlorine added at one time, and supplementary addition is required, which increases the complexity and investment cost of the system. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a method for calculating and regulating the amount of chlorine added in a water plant, which can achieve accurate calculation and real-time regulation of the amount of chlorine added.

[0005] To achieve the above object, the present invention has adopted the following technical scheme: A method for calculating and controlling the amount of chlorine added in a water plant comprises the following steps: S1. Prepare raw water with different typical values ​​of water quality parameters for beaker experiment, use beaker experiment to obtain the chlorine demand under different water quality parameters, and establish a mathematical model of chlorine demand under different water quality parameters based on regression analysis of a large amount of data obtained from beaker experiment; S2. Take water samples near the water inlet in the clean 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 attenuation curve; S3. Obtain the average water volume treated per hour by the water plant; or use regression analysis to establish a functional relationship between the water volume and the time of the clean water tank based on the historical data of the changes in the water volume and the water volume of the clean water tank over time; S4. Calculate the hydraulic retention time of the clean water tank using the water treatment volume, or calculate the water inflow and outflow of the clean water tank at a certain moment using the functional relationship between the water inflow and outflow and time, and calculate the hydraulic retention time of the tracked water body in the clean water tank based on the water inflow and outflow of the clean water tank; S5. Calculate the hydraulic retention time T required for the raw water to reach the water plant outlet after chlorination; S6. Using the residual chlorine decay curve obtained in step S2, calculate the residual chlorine consumed by the raw water during the hydraulic retention time T, i.e., the residual chlorine consumption; calculate the chlorine demand based on the mathematical model of the chlorine demand obtained in step S1 according to the current water quality index; calculate the chlorine addition amount using the chlorine addition amount calculation formula: Chlorine addition amount = chlorine demand + residual chlorine consumption + residual chlorine balance; S7. Real-time detection of residual chlorine in factory water to ensure that the residual chlorine value of factory water meets the standard. When the residual chlorine value is abnormal, timely warning is given. At the same time, the residual chlorine is fed back to the control system to adjust the chlorine addition amount in real time.

[0006] In the above method, the water quality parameters described in step S1 refer to organic matter content, ammonia nitrogen, and pH; a large amount of data obtained through beaker experiments is used to construct a functional relationship between pH, organic matter content, ammonia nitrogen and raw water chlorine demand, and the best approximation function Y=f(X) is obtained, which is the optimal dosage model under the raw water quality parameter X; the function is used to calculate the optimal chlorine demand Y of a specific volume of raw water under specific water quality parameters.

[0007] The parallel first-order reaction model described in step S2 is as follows: , In the formula, t Represents the reaction time, x It indicates the percentage of the initial residual chlorine concentration participating in the fast reaction to the total initial residual chlorine concentration. C 0 is the total initial residual chlorine concentration, k f is the fast reaction decay constant of residual chlorine, k s is the residual chlorine slow reaction decay constant; Least squares fitting k f and k s Two parameters, get k s and k f , the residual chlorine concentration can be obtained C Functional relationship about time t. Initial residual chlorine concentration C 0 Subtract the residual chlorine concentration at time t C The elapsed time can be obtained tResidual chlorine consumption.

[0008] The initial residual chlorine concentration participating in the fast reaction is the residual chlorine concentration participating in the reaction within 0-30 minutes. x It is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 minutes and the initial residual chlorine concentration. The calculation formula is as follows: x=y(C0-C 30 ) / C 0， In the formula, C 0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration after 30 minutes. y As the adjustment coefficient, take 1.15.

[0009] Since the clean water tank contains a small amount of impurities, which will affect the residual chlorine decay after chlorination, water samples are taken near the water inlet of the clean water tank in order to better simulate the residual chlorine decay process in the clean water tank.

[0010] The residual chlorine mentioned here refers to Cl2, HClO and ClO - The sum of the concentrations.

[0011] The method for calculating the hydraulic retention time of the clean water tank using the water treatment volume in step S4 is: obtain the average water treatment volume per hour of the water plant Q h and the volume of the clean water tank V , then the hydraulic retention time of this period is HRT(h) for: .

[0012] In step S4, the hydraulic retention time of the tracked water body in the clean water tank is calculated according to the water inflow and outflow of the clean water tank, and the method is: The volume of water in the clear water tank at the initial time V tk , take the water inflow of the clean water tank at a certain moment as the tracking object, and calculate the hydraulic retention time in the clean water tank. There are two situations: (1) When the water flow in and out of the clean water tank is always the same and the water volume in the clean water tank remains unchanged, , In the formula, HRT tk is the hydraulic retention time in the clean water tank at a certain moment, Q (tk) is the inflow or outflow of the clean water tank at the current time, and the two are equal at this time; (2) When the water flow rate in and out of the clean water tank changes, and the water inlet tracking object entering the clean water tank has not been discharged from the clean water tank before the hydraulic retention time of the clean water tank changes, the calculation method is as follows: Using the correlation function between the water inflow and outflow in one day and the time change obtained in step S3, At any time interval Δ t The change in the volume of the clear water tank is Δ V It can be expressed as: , in s is the integrating variable, representing time, Q in ( s ) is the functional relationship between the water inflow of the clean water tank and time, Q out ( s ) is the functional relationship between the water output of the clean water tank and time. The average flow of water inflow and outflow during this period is: , , In the formula, is the average water inlet flow at time t, is the average outflow flow at time t; The total average flow is: , The hydraulic retention time in the current period can be approximated as: , Said V ( t ) is the volume of water in the clean water pool at the previous moment.

[0013] The above-mentioned tracking object preferably takes the volume of water passing through a certain detection period as a slice unit. For example, if the flow detection period through the chlorination point is 2 minutes, the volume of water passing through the detection period is a slice unit, and the hydraulic retention time is sliced ​​and calculated.

[0014] The calculation method for the time T required for the raw water of the slice unit volume to reach the water plant outlet after chlorination is as follows: , In the formula, T 入 The time required for the calculation slice unit to enter the clean water tank is calculated as follows: , in, Q in ( t) is the flow rate of the clean water tank inlet after adding the drug, V 切 is the volume of chlorinated water added during the test period; T 出 The time required for the calculation slice unit to flow out of the clean water tank is calculated as follows: , in, Q out ( t ) is the water flow rate of the clean water tank when the slice unit reaches the outlet of the clean water tank after staying in the clean water tank, HRT 切 is the hydraulic retention time of the slice unit in the clean water tank.

[0015] The residual chlorine content in step S6 is the residual chlorine content of the water after chlorination at the water plant outlet, and the residual chlorine range is 0.3-0.5 mg / L.

[0016] In step S7, the residual chlorine value of the factory water should be greater than or equal to 0.3 mg / L according to my country's drinking water hygiene standards. The water supply company generally controls it between 0.3-0.5 mg / L. Therefore, the residual chlorine range of the factory water is 0.3-0.5 mg / L.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention can accurately calculate the amount of chlorine added, and can adjust the amount of chlorine added in real time according to changes in water quality, the hydraulic retention time of the clean water tank and the residual chlorine content. Compared with the traditional chlorination method, it reduces the waste of drugs, helps to reduce the use of disinfectants, thereby reducing operating costs and achieving energy-saving and environmental protection effects.

[0018] (2) The present invention can monitor the residual chlorine content at the water plant outlet and the inlet and outlet flow of the clear water tank, scientifically direct the dosage of disinfectant in the water plant, and effectively ensure that the residual chlorine concentration in the water is within a safe range, thereby avoiding water pollution caused by excessive residual chlorine and ensuring that the water quality meets the disinfection standard, thereby improving the safety of drinking water. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments. The specific implementation methods described herein are only used to illustrate and explain the present invention and do not constitute a limitation of the present invention.

[0021] Embodiment 1 A method for calculating and controlling the amount of chlorine added in a water plant comprises the following steps: S1. Prepare raw water with different typical values ​​of water quality parameters for beaker experiment, use beaker experiment to obtain the chlorine demand under different water quality parameters, and establish a mathematical model of chlorine demand under different water quality parameters based on regression analysis of a large amount of data obtained from beaker experiment: (1) Take raw water, measure the water quality parameters (organic matter content, ammonia nitrogen, pH, etc.) of the raw water, and take water samples with different water quality parameters to repeat the experiment; (2) Add different amounts of sodium hypochlorite solution (or other disinfectants) to each beaker and record the concentration and volume of the added sodium hypochlorite solution. Stir the water sample slowly with a stirrer and then let it settle for a while to allow the disinfectant to fully react with the substances in the water. (3) Stop stirring the paddles, keep the beakers away from light for 30 minutes, and then use an appropriate chemical method (such as iodine titration) to determine the amount of residual chlorine in each beaker after the reaction. (4) Subtract the remaining chlorine from the added chlorine to obtain the chlorine demand. Record the chlorine demand for each water sample at different sodium hypochlorite addition amounts.

[0022] A large amount of data obtained from the beaker experiment was subjected to regression analysis to construct the functional relationship between pH, organic matter content, ammonia nitrogen and raw water chlorine demand, and obtain the best approximation function Y = f (X). In the best approximation function f (X), X is a three-dimensional variable, and the relationship between raw water chlorine demand and water quality parameters is nonlinear. f (X) is a three-variable nonlinear regression model. Y is the best dosage model under raw water quality parameter X.

[0023] S2. Take water samples near the water inlet in the clean 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 attenuation curve: (1) Take a water sample from the clean water tank near the water inlet, add the water sample into a brown container, and place the brown container in a constant temperature box with the temperature kept constant at 13-19°C.

[0024] The purpose of controlling the temperature to be constant is to ensure that the residual chlorine decay can be carried out at the same temperature and the various measurement data are not affected by temperature changes.

[0025] (2) The above water samples were subjected to the determination of residual chlorine concentration C (mg / L) at different times t, where different times t refer to the sampling and detection times at 10 min, 20 min, 30 min, 60 min, 90 min, 120 min, 150 min, 180 min, and 240 min, and the parallel first-order reaction model of the following formula was used to fit the data: , In the formula, t Represents the reaction time, xIt indicates the percentage of the initial residual chlorine concentration participating in the fast reaction to the total initial residual chlorine concentration. C 0 is the total initial residual chlorine concentration, k f is the fast reaction decay constant of residual chlorine, k s is the residual chlorine slow reaction decay constant.

[0026] There are two types of reactions in the residual chlorine decay in water of poor quality. One is a rapid reaction, which is usually completed within 0.5 hours and consumes 30%-60% of the residual chlorine. The residual chlorine rapid reaction decay constant is k f Corresponding to this process; the other is a slow reaction, which generally takes 10 to 20 hours to complete. The residual chlorine slow reaction decay constant k s Corresponding to this process.

[0027] Least squares fitting k f and k s Two parameters, get k s and k f , the residual chlorine concentration can be obtained C Functional relationship about time t. Initial residual chlorine concentration C 0 Subtract the residual chlorine concentration at time t C The residual chlorine consumption after time t can be obtained.

[0028] The initial residual chlorine concentration participating in the fast reaction is the residual chlorine concentration participating in the reaction within 0-30 minutes. x It is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 minutes and the initial residual chlorine concentration. The calculation formula is as follows: x=y(C0-C 30 ) / C 0， In the formula, C 0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration at 30 minutes, y is the adjustment coefficient, which is 1.15. The residual chlorine refers to Cl2, HClO and ClO - The sum of the concentrations.

[0029] S3. Obtain the average amount of water treated per hour by the water plant.

[0030] S4. Calculate the hydraulic retention time of the clean water tank using the water treatment volume: Get the average amount of water treated per hour by the water plantQ h and the volume V of the clear water tank, then the hydraulic retention time during this period is HRT (h) for: .

[0031] S5. Calculate the hydraulic retention time T required for raw water to reach the water plant outlet after chlorination: T= HRT(h) +T 出 +T 入 , HRT(h) is the hydraulic retention time in the clean water tank, T 入 It is the time required for raw water to flow from the chlorination point into the clean water tank after chlorination, T 出 T is the time required for raw water to flow from the outlet of the clean water tank to the outlet of the water plant after chlorination. 入 and T 出 The calculation formula is as follows: T 入 =V 入水管 / Q h , T 出 =V 出水管 / Q h , Where V 入水管 V is the volume of the pipeline from the chlorination point to the water plant inlet, 出水管 is the volume of the pipeline from the clear water tank outlet to the water plant outlet, Q h is the average water volume processed by the water plant.

[0032] S6. Using the residual chlorine decay curve obtained in step S2, calculate the amount of residual chlorine consumed during the hydraulic retention time T; calculate the chlorine demand based on the mathematical model of chlorine demand obtained in step S1 according to the current water quality index; calculate the chlorine addition amount using the chlorine addition amount calculation formula: Chlorine addition amount = chlorine demand + residual chlorine consumption + residual chlorine balance; The residual chlorine content is the residual chlorine content of the water after chlorination at the water plant outlet, and the residual chlorine range is 0.3-0.5 mg / L.

[0033] S7. Real-time detection of residual chlorine in water leaving the factory to ensure that the residual chlorine value of the water leaving the factory meets the standard. When the residual chlorine value is abnormal, timely warning is issued. At the same time, the residual chlorine is fed back to the control system to adjust the chlorine addition amount in real time: According to my country's drinking water hygiene standards, the residual chlorine value of factory water should be greater than or equal to 0.3 mg / L. Water supply companies generally control it between 0.3-0.5 mg / L. Therefore, the residual chlorine range of factory water is 0.3-0.5 mg / L.

[0034] Embodiment 2 A method for calculating and controlling the amount of chlorine added in a water plant comprises the following steps: S1. The same as step S1 of Example 1; S2. The same as step S2 of Example 1; S3. Based on the historical data of the change of water inflow and outflow of the clean water tank over time, the functional relationship between the water inflow and outflow of the clean water tank and time is established by regression analysis: (1) Data collection: Flow sensors are installed at the water inlet and outlet of the clean water tank to monitor and record the inlet and outlet flow rates in real time. The inlet and outlet flow data of the clean water tank are obtained for each time period (e.g., every minute) within a year. These data include timestamps and corresponding flow values. (2) Check the missing values ​​in the data and choose to fill (such as using the mean, median, previous value, etc.) or delete the missing data points as appropriate. Divide the dataset into a training set and a test set (for evaluating model performance). Typically, 70%-80% of the data is used for training and the remaining data is used for testing; (3) Use the linear regression method to fit the curve. The independent variable (x) is time, the dependent variable (y) is the inlet flow rate or outlet flow rate, and a linear regression equation is established; (4) Use the test set data to evaluate the accuracy of the curve. Compare the fitted equation curve with the actual traffic data, and calculate the error between the predicted value and the actual value. Commonly used evaluation indicators include mean square error (MSE), mean absolute error (MAE), R2 score, etc. to improve the fitting accuracy.

[0035] S4. Calculate the water inflow and outflow of the clean water tank at a certain moment using the functional relationship between the water inflow and outflow and time, and calculate the hydraulic retention time of the tracked water body in the clean water tank based on the water inflow and outflow of the clean water tank: In order to make the hydraulic retention time of the clean water tank more accurate and lay a foundation for accurately calculating the amount of chlorine added, this embodiment combines the water inlet and outlet curves of the clean water tank to calculate the hydraulic retention time T of the water after chlorination at the current time in the clean water tank. The steps are as follows: (1) Install a level meter in the clean water tank to obtain the initial volume of water in the clean water tank. Assume that the geometry of the tank is known and the water volume Vt Through the water level W and bottom area S To calculate: Vt = S × W ; (2) Know the volume of water in the clean water tank at the initial time V tk , the following formula can be used to calculate the hydraulic retention time in the clear water tank at the current time: Take the water inflow of the clean water tank at a certain moment as the tracking object and calculate the hydraulic retention time in the clean water tank. There are two situations: ①When the water flow in and out of the clean water tank is always consistent and the water volume in the clean water tank remains unchanged, , In the formula, HRT t k is the hydraulic retention time of the clean water tank, Q (tk) is the inflow or outflow of the clean water tank at the current time, and the two are equal at this time; ② When the water flow rate in and out of the clean water tank or the volume of the clean water tank changes (that is, the hydraulic retention time of the clean water tank changes), and the water inlet tracking object entering the clean water tank has not been discharged from the clean water tank before the hydraulic retention time of the clean water tank changes, the calculation method is as follows: The water inflow and outflow in one day obtained in step S3 and the time change have a related functional relationship. t The change in the volume of the clear water tank is Δ V It can be expressed as: , in s is the integrating variable, representing time, Q in ( s ) is the functional relationship between the water inflow of the clean water tank and time, Q out ( s ) is the functional relationship between the water output of the clean water tank and time. The average flow of water inflow and outflow during this period is: , , In the formula, is the average water inlet flow at time t, is the average outflow rate at time t;

[0036] The total average flow is: , The hydraulic retention time of the current period can be approximated as: , V ( t ) is the volume of water in the clear water pool at the previous moment. Theoretically, the time step is calculated t The smaller the interval time, the more accurate the calculation. Preferably, the calculation time step t The interval time should be 2min.

[0037] Therefore, the calculation formula for the hydraulic retention time of the tracked water body in the clear water tank is as follows: If the hydraulic retention time is changed once and then not changed again: , , ; Then after the hydraulic retention time changes n times: , , ; Hydraulic retention time of the tracked unit in the clear water tank HRT : , Note: The value of n in the formula needs to be determined according to actual conditions. t 0 is the moment when the tracked water body enters the clean water tank; t'0 is the last moment when the initial hydraulic retention time of the clean water tank remains unchanged before it changes; t n is the moment when the hydraulic retention time of the clean water tank changes n times; t' n-1 It is the last moment when the hydraulic retention time after the n-1th change remains unchanged after the tracked water body enters the clean water tank; V tn t n The volume of water in the clean water tank at all times; V ( s n ) is in t n The volume that the water body being tracked needs to pass through in the clean water tank at any given moment is calculated by the above formula; ∆ V tn for t n - t’ n-1 The change in volume of the clean water tank at a given moment is the volume of the total water flow in the clean water tank that increases or decreases; ∆ V n for t n - t’ n-1 The effective volume of the clear water tank changes at every moment, which is the volume of the remaining water that the tracked water body needs to pass through in the clear water tank; HRT an The tracked unit is n The time required to drain the clean water tank from the moment; In t n Average flow rate in the clear water tank at any given moment, in m 3 / h.

[0038] For example: After the prediction and calculation of the water inlet and outlet function relationship of the clean water tank, at 10:00, the tracked doped water body enters the clean water tank. From 10:00 to 10:30, the hydraulic retention time of the clean water tank remains at 2h, and the volume remains unchanged, which is 500m 3 , the average flow is 250m 3 / h; at 10:32, the hydraulic retention time of the clear water tank became 1.8h and the volume became 450m 3 , the average flow is 270m 3 / h; 10:34 The hydraulic retention time of the clean water tank changes to 1.5h, and the volume changes to 400m 3 , the average flow is 300m 3 / h, after which the hydraulic retention time remains unchanged. The retention time calculation process of the tracked water body in the clear water tank is as follows: , ; , , ; The residence time of the tracked water body in the clean water tank T for: , That is, after the tracked water body enters the clear water tank at 10:00, the hydraulic retention time is about 1.52h, and it is expected to be discharged from the clear water tank at 11:31.

[0039] S5. Calculate the hydraulic retention time T required for raw water to reach the water plant outlet after chlorination: In a fixed time period, the water flow rate of the current time period can be intercepted to calculate the water volume of the clean water tank in the current time period. This volume is a calculation slice unit. Assuming that the intercepted time period is from t0 to t1, the volume of the slice unit can be calculated using the following formula: , In the formula, t s and t E are the times corresponding to the interception moments respectively; Q in ( t ) dt Indicates the change of water inlet flow rate over time; V 切 is the volume of the calculated grid cell.

[0040] The time required for the raw water of this slice unit volume to reach the water plant outlet after chlorinationT The calculation method is as follows: , In the formula, T 入 The time required for the calculation slice unit to enter the clean water tank is calculated as follows: , in, Q in ( t ) is the flow rate at the water inlet of the clean water tank after adding the drug; T 出 The time required for the calculation slice unit to flow out of the clean water tank is calculated as follows: , in, Q out ( t ) is the water outflow rate of the clear water tank when the slice unit reaches the outlet of the clear water tank after staying in the clear water tank.

[0041] HRT 切 The hydraulic retention time of the calculated slice unit in the clean water tank is calculated by using the formula in case ① in step S4 (2) if the predicted hydraulic retention time of the clean water tank remains unchanged. If the slice unit does not leave the clean water tank before the predicted hydraulic retention time of the clean water tank changes, the formula in case ② in step S4 (2) can be used for calculation.

[0042] Preferably, the fixed time period for calculating the water volume of the slice unit is 2 minutes.

[0043] S6. Using the residual chlorine attenuation curve obtained in step S2, calculate the residual chlorine consumed by the chlorinated water of the slice unit volume within the time T when it reaches the water plant outlet, that is, the residual chlorine consumption; calculate the chlorine demand based on the mathematical model of the chlorine demand obtained in step S1 according to the current water quality index; finally, within the calculation time period (2 minutes) of the slice unit, the calculation formula for the chlorine addition amount of the raw water is as follows: Chlorine addition amount = chlorine demand + residual chlorine consumption + residual chlorine balance; The residual chlorine content is the residual chlorine content of the water after chlorination at the water plant outlet, and the residual chlorine range is 0.3-0.5 mg / L.

[0044] The water quality index at the chlorination point is tested once a day, and the required chlorine amount is calculated based on the test results of the day.

[0045] S7. Real-time detection of residual chlorine in water leaving the factory to ensure that the residual chlorine value of the water leaving the factory meets the standard. When the residual chlorine value is abnormal, timely warning is issued. At the same time, the residual chlorine is fed back to the control system to adjust the chlorine addition amount in real time: According to my country's drinking water hygiene standards, the residual chlorine value of factory water should be greater than or equal to 0.3 mg / L. Water supply companies generally control it between 0.3-0.5 mg / L. Therefore, the residual chlorine range of factory water is 0.3-0.5 mg / L.

[0046] The above description is only a specific implementation mode of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating and controlling the amount of chlorine added in a water plant, characterized in that: The steps include: S1. Prepare raw water with different typical values ​​of water quality parameters for beaker experiment, use beaker experiment to obtain the chlorine demand under different water quality parameters, and establish a mathematical model of chlorine demand under different water quality parameters based on regression analysis of a large amount of data obtained from beaker experiment; S2. Take water samples near the water inlet in the clean 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 attenuation curve; S3. Obtain the average water volume treated per hour by the water plant; or use regression analysis to establish a functional relationship between the water volume and the time of the clean water tank based on the historical data of the changes in the water volume and the water volume of the clean water tank over time; S4. Calculate the hydraulic retention time of the clean water tank using the water treatment volume, or calculate the water inflow and outflow of the clean water tank at a certain moment using the functional relationship between the water inflow and outflow and time, and calculate the hydraulic retention time of the tracked water body in the clean water tank based on the water inflow and outflow of the clean water tank; S5. Calculate the hydraulic retention time T required for the raw water to reach the water plant outlet after chlorination; S6. Using the residual chlorine decay curve obtained in step S2, calculate the residual chlorine consumed by the raw water during the hydraulic retention time T, i.e., the residual chlorine consumption; calculate the chlorine demand based on the mathematical model of the chlorine demand obtained in step S1 according to the current water quality index; calculate the chlorine addition amount using the chlorine addition amount calculation formula: Chlorine addition amount = chlorine demand + residual chlorine consumption + residual chlorine balance; S7. Real-time detection of residual chlorine in factory water to ensure that the residual chlorine value of factory water meets the standard. When the residual chlorine value is abnormal, timely warning is given. At the same time, the residual chlorine is fed back to the control system to adjust the chlorine addition amount in real time.

2. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 1, characterized in that: The water quality parameters described in step S1 refer to organic matter content, ammonia nitrogen, and pH. A large amount of data obtained through the beaker experiment is used to construct a functional relationship between pH, organic matter content, ammonia nitrogen and raw water chlorine demand, and obtain the best approximation function Y=f(X), which is the optimal dosage model under the raw water quality parameter X.

3. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 1, characterized in that: The parallel first-order reaction model described in step S2 is as follows: ， In the formula, t Represents the reaction time, x It indicates the percentage of the initial residual chlorine concentration participating in the fast reaction to the total initial residual chlorine concentration. C 0 is the total initial residual chlorine concentration, k f is the fast reaction decay constant of residual chlorine, k s is the residual chlorine slow reaction decay constant; x It is the ratio of the initial residual chlorine concentration minus the residual chlorine concentration sampled at 30 minutes and the initial residual chlorine concentration. The calculation formula is as follows: x = y ( C 0 - C 30 ) / C 0 ， In the formula, C 0 is the total initial residual chlorine concentration, C 30 is the residual chlorine concentration after 30 minutes. y is the adjustment coefficient, which is taken as 1.15; Least squares fitting k f and k s Two parameters, get k s and k f , the residual chlorine concentration can be obtained C The functional relationship of time t is as follows: initial residual chlorine concentration C 0 Subtract the residual chlorine concentration at time t C The residual chlorine consumption after time t can be obtained.

4. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 1, characterized in that: The method for calculating the hydraulic retention time of the clean water tank using the water treatment volume in step S4 is: obtain the average water treatment volume per hour of the water plant Q h and the volume of the clear water tank V , then the hydraulic retention time of this period is HRT(h) for: 。 5. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 4, characterized in that: Step S5 calculates the hydraulic retention time T required for the raw water to reach the water plant outlet after chlorination: T= HRT(h) +T 出 +T 入 , HRT(h) is the hydraulic retention time in the clean water tank, T 入 It is the time required for raw water to flow from the chlorination point into the clean water tank after chlorination, T 出 It is the time required for raw water to flow from the outlet of the clean water tank to the outlet of the water plant after chlorination.

6. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 1, characterized in that: In step S4, the hydraulic retention time of the tracked water body in the clean water tank is calculated according to the water inflow and outflow of the clean water tank, and the method is: The volume of water in the clear water tank at the initial time V tk , take the water inflow of the clean water tank at a certain moment as the tracking object, and calculate the hydraulic retention time in the clean water tank. There are two situations: (1) When the water flow in and out of the clean water tank is always consistent and the water volume in the clean water tank remains unchanged, ， In the formula, HRT tk is the hydraulic retention time in the clean water tank at a certain moment, Q (tk) is the inflow or outflow of the clean water tank at the current time, and the two are equal at this time; (2) When the water flow rate in and out of the clean water tank changes, and the water inlet tracking object entering the clean water tank has not been discharged from the clean water tank before the hydraulic retention time of the clean water tank changes, the calculation method is as follows: The water inflow and outflow in one day obtained in step S3 and the time change have a related functional relationship. At any time interval Δ t The change in the volume of the clear water tank is Δ V It can be expressed as: ， in s is the integrating variable, representing time, Q in ( s ) is the functional relationship between the water inflow of the clean water tank and time, Q out ( s ) is the functional relationship between the water output of the clean water tank and time. The average flow of water inflow and outflow during this period is: ， ， In the formula, is the average water inlet flow at time t, is the average outflow flow at time t; The total average flow is: ， The hydraulic retention time in the current period can be approximated as: ， Said V ( t ) is the volume of water in the clean water pool at the previous moment.

7. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 1, characterized in that: In step S4, the volume of water passing through the tracked water body during a certain detection period is taken as a slice unit, and the slice calculation of the hydraulic retention time is performed.

8. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 7, characterized in that: The calculation method of the time T required for the raw water of the slice unit volume to reach the water plant outlet after chlorination in step S5 is as follows: ， In the formula, T 入 The time required for the calculation slice unit to enter the clean water tank is calculated as follows: ， in, Q in ( t ) is the flow rate of the clean water tank inlet after adding the drug, V 切 is the volume of chlorinated water added during the test period; T 出 The time required for the calculation slice unit to flow out of the clean water tank is calculated as follows: ， in, Q out ( t ) is the water flow rate of the clean water tank when the slice unit reaches the outlet of the clean water tank after staying in the clean water tank, HRT 切 is the hydraulic retention time of the slice unit in the clean water tank.

9. A method for calculating and controlling the amount of chlorine added in a waterworks according to claim 1, characterized in that: The residual chlorine content in step S6 is the residual chlorine content of the water after chlorination at the water plant outlet, and the residual chlorine range is 0.3-0.5 mg / L.

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