Accurate alkali aluminum adding control method and system for raw water treatment

Abstract

The invention provides a control method and system for accurately adding alkali aluminum for raw water treatment. The method comprises the steps of real-time data acquisition, model establishment and parameter correction, adding flow calculation and automatic control of an adding pump. According to the method, an adding flow calculation model is established, model parameters are corrected according to the change trend of real-time data such as turbidity and flow, required adding unit consumption and adding flow are calculated, the calculation result of the model serves as an expected value of a control target, the working frequency of a dosing pump is automatically controlled and adjusted through negative feedback, the current value tends to the expected value, and the control precision is improved. And finally, the requirements of real-time sensing, quick response and accurate control are met. The invention provides a technical scheme for ensuring the treatment quality, improving the treatment efficiency and reducing the energy consumption in the raw water treatment process, so that the operation cost of a water plant is effectively reduced, and the stability of a water purification system is improved. Meanwhile, the precisely-controlled feeding model has general practicability and is suitable for feeding scenes of the same type of processes.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a precise alkali-aluminum dosing control method and system for raw water treatment. Background Art

[0002] With the continuous improvement of people's living standards, the quality and quantity of treated water in urban raw water treatment plants are increasing year by year. In the process of raw water treatment, the addition of alkali aluminum is a key link.

[0003] Alkali aluminum, the full name of which is basic aluminum oxide, has an adsorption effect and can condense colloidal particles that are not easy to precipitate in water to form larger flocs, which are convenient for separation and precipitation from water. Due to factors such as water quality and water flow, the existing alkali aluminum dosing system often relies on manpower, and there are problems such as unstable dosing and inaccurate control, which not only affects the effect of water treatment, but also causes waste of resources. Summary of the invention

[0004] The first object of the present invention is to provide a method for accurately controlling the addition of alkali aluminum for raw water treatment in view of the deficiencies in the prior art.

[0005] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0006] A precise dosing control method of alkali aluminum for raw water treatment, including real-time data acquisition, model establishment and model parameter correction, calculation of dosing flow rate and automatic control of dosing pump;

[0007] S1. Real-time data collection:

[0008] According to the process control requirements, the target parameters are periodically sampled and then filtered by the limiting filter method, and then the valid data Z1, Z2, Z3, ..., Z n ;

[0009] S2. Model establishment and model parameter correction

[0010] S21. Establish a universal calculation model applicable to the dosing system in the raw water treatment process. The model is used to analyze the changing trend of the monitoring data in the current period and calculate the dosing unit consumption and dosing flow required for the sedimentation tank. The input of the model includes the sampling value, upper and lower limits of the target parameters, and the flow ratio.

[0011] S22. Model parameter correction

[0012] (1) Correction threshold coefficient Ka

[0013] According to whether the data in the continuous time period T is within the threshold range of the process requirements, the adjustment coefficient Ka is set;

[0014] (2) Corrected trend coefficient Kb

[0015] The model samples the indicators with a period of t, sorts and compares the sampled data, and adjusts the adjustment coefficient Kb according to the change trend of the data in the continuous time period T;

[0016] (3) Corrected flow coefficient Kc

[0017] Calculate the real-time ratio of the current inlet flow rate of the reaction tank to the design scale flow rate, determine whether it is running at full load, and set the adjustment coefficient Kc;

[0018] S3. Calculate the dosage required to treat a unit mass of water at the next moment. The calculation formula is:

[0019] M k =M k-1 ×[(Ka+Kb+Kc)×R+1]

[0020] in:

[0021] M k The dosage required to treat a unit mass of water at the next moment;

[0022] M k-1 The dosage required to treat a unit mass of water at the last moment;

[0023] R is the upper limit of the given change range;

[0024] Calculate the addition flow rate F, the calculation formula is as follows:

[0025]

[0026] in:

[0027] F is the alkali aluminum addition flow rate, in L / h;

[0028] f1 is the inflow flow rate of the sedimentation tank, in m 3 / h;

[0029] M k The dosage required to treat a unit mass of water, in mg / L;

[0030] ρ is the density of the solution in which the flocculant is dissolved, in kg / L;

[0031] λ is the concentration of the solution in which the flocculant is dissolved;

[0032] S4, judging whether the dosing flow rate value calculated in step S3 is greater than the current dosing flow rate, if yes, continue to judge whether the dosing pump put into operation is already running at the highest frequency, if yes, put the standby pump into operation, otherwise increase the working frequency of the dosing pump already put into operation;

[0033] Determine whether the dosing flow rate value calculated in step S3 is less than the current dosing flow rate. If so, continue to determine whether the dosing pumps in operation are already running at the lowest frequency. If so, stop one of the pumps and switch it to standby, otherwise reduce the operating frequency of the dosing pumps that have been put into operation; if the calculated value is equal to the current value, it is considered that there is no need to adjust the dosing pump, and return to step S1 after a certain delay.

[0034] Another object of the present invention is to provide a precise alkali-aluminum dosing control system for raw water treatment.

[0035] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0036] A precise alkali-aluminum dosing control system for raw water treatment, comprising: an inlet water online flow meter, an online turbidity monitoring instrument, a variable frequency dosing pump, a PLC control cabinet, and a host computer, characterized in that: the host computer executes the precise alkali-aluminum dosing control method for raw water treatment as described above, so as to obtain real-time data of the inlet water online flow meter and the turbidity online monitoring instrument through the PLC control cabinet, and transmit the processed data to the host computer for processing, and the host computer sends a signal for adjusting the working frequency of the variable frequency dosing pump to the PLC control cabinet based on the data to adjust the flow of alkali-aluminum added to the sedimentation tank.

[0037] The inlet water online flow meter is installed on the inlet pipe of the sedimentation reaction tank to measure the inlet water flow rate;

[0038] The turbidity online monitoring instrument is installed in the sedimentation reaction tank to monitor the turbidity of the water in the sedimentation reaction tank;

[0039] The variable frequency dosing pump is installed on the dosing pipeline of the precipitation reaction tank, and is used to add alkali aluminum to the precipitation reaction tank. The dosing pump has variable frequency capability and can control the dosing flow rate; the automatic control dosing pump (variable frequency dosing pump) refers to a closed-loop control with a negative feedback mechanism. The dosing flow rate calculated by the model is used as the expected value and compared with the current value. If it is less than the current value, the working frequency of the dosing pump is reduced; if it is greater than the current value, the working frequency of the dosing pump is increased until the current value is equal to the expected value. The instructions for increasing or decreasing the frequency are sent to the dosing pump by the PLC.

[0040] The sedimentation reaction tank is set at the front end of the water treatment pipeline of the whole plant, directly connected to the water inlet pipeline or indirectly connected through the water distribution well. The sedimentation reaction tank is mainly used to precipitate large particles in the water. Adding flocculants such as alkali aluminum into the tank can absorb suspended impurities in the water, accelerate the sedimentation process and enhance the sedimentation efficiency;

[0041] The PLC control cabinet is set up in the control layer of the water plant. The cabinet contains a controller (PLC), power supply, industrial gateway, switch and other communication equipment. It is an integrated control unit commonly used in industrial control. The PLC control cabinet is connected to the host computer through Ethernet. There is an acquisition module in the PLC control cabinet, which is electrically connected to the variable frequency dosing pump, the water inlet online flow meter, and the turbidity online monitoring instrument respectively; the controller (PLC) can collect the water inlet flow and turbidity according to the signal acquisition module, and adjust the working frequency of the variable frequency dosing pump according to the turbidity signal fed back by the turbidity detector, so as to adjust the flow rate of alkali aluminum added to the sedimentation tank.

[0042] High-performance sensors are used to monitor in real time and periodically collect signals such as raw water turbidity. The PLC is connected to each sensor through the RS485 serial port to achieve real-time communication. The PLC cleans the collected data and sends the cleaned data to the host computer as the input of the model.

[0043] Data cleaning uses the limiting filter method to sample the collected data at intervals of 30 seconds. The sampling value deviation is valid within ±0.005, and the value exceeding ±0.005 is considered as a disturbance and discarded. The data cleaned in this way is used for subsequent analysis and processing;

[0044] The host computer, which is installed in the control room of the water plant, refers to an industrial computer capable of running a computer monitoring system, and has the functions of data monitoring, remote control, data statistics and trend analysis, recording alarms and operations.

[0045] The present invention provides a precise dosing control method and system for raw water treatment. The precise dosing control system includes an inlet online flow meter, a turbidity online monitoring instrument, a variable frequency dosing pump, a PLC control cabinet, and a host computer. The precise dosing control method includes real-time data acquisition, model establishment and parameter correction, calculation of dosing flow, and automatic control of dosing pumps. The present invention establishes a dosing flow calculation model, corrects model parameters according to the change trend of real-time data such as turbidity and flow, calculates the required dosing unit consumption and dosing flow, and uses the calculation result of the model as the expected value of the control target. The working frequency of the dosing pump is adjusted through negative feedback automatic control to make the current value tend to the expected value, and finally achieves the requirements of real-time perception, rapid response, and precise control. The present invention provides a technical solution for the raw water treatment process that not only ensures the treatment quality, but also improves the treatment efficiency and reduces energy consumption, effectively reduces the operating cost of the water plant, and improves the stability of the water purification system. At the same time, the precise control dosing model involved in the present invention has universal practicality and is suitable for dosing scenarios of the same type of process.

[0046] Specifically, the present invention has the following beneficial effects:

[0047] 1) By establishing a control model and calculating the required unit consumption, accurate control of alkali and aluminum addition is achieved, thus improving the water treatment effect;

[0048] 2) By collecting data in real time and adjusting the model through feedback, the system can be more adapted to the actual operation situation, thus improving the stability and reliability of the system;

[0049] 3) By precisely controlling the amount of alkali aluminum added, energy consumption and resource waste are reduced, achieving the goals of low turbidity and low consumption, with significant economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a structural diagram of the precise alkali-aluminum dosing control system for raw water treatment provided by the present invention.

[0051] In the figure: 1-raw water sedimentation tank; 2-dosing pump; 3-dosing pipeline; 4-water inlet pipeline; 5-water inlet online flow meter; 6-turbidity online monitor; 7-PLC; 8-host computer; 9-data acquisition module; 10-PLC control cabinet;

[0052] Figure 2 The present invention provides a working flow chart of the precise alkali-aluminum dosing control method for raw water treatment. DETAILED DESCRIPTION

[0053] A precise dosing control method of alkali aluminum for raw water treatment, including real-time data acquisition, model establishment and model parameter correction, calculation of dosing flow rate and automatic control of dosing pump;

[0054] S1. Real-time data collection:

[0055] According to the process control requirements, the target parameters are periodically sampled and then filtered by the limiting filter method, and then the valid data Z1, Z2, Z3, ..., Z n ;

[0056] S2. Model establishment and model parameter correction

[0057] S21. Establish a universal calculation model applicable to the dosing system in the raw water treatment process. The model is used to analyze the changing trend of the monitoring data in the current period and calculate the dosing unit consumption and dosing flow required for the sedimentation tank. The input of the model includes the sampling value, upper and lower limits of the target parameters, and the flow ratio.

[0058] S22. Model parameter correction

[0059] (1) Correction threshold coefficient Ka

[0060] The adjustment coefficient Ka is set according to whether the data of the target parameter in the continuous time period T is within the threshold range required by the process.

[0061] If the indicator is within the preset range for a period of time T, that is, Z min <Z1,Z2,Z3,...,Z n <Z max , t≥T, then set the coefficient Ka=-0.3;

[0062] If the indicator is higher than the set upper limit for a period of time T, that is, Z1, Z2, Z3, ..., Z n >Z max , t≥T, then set the coefficient Ka=0.3;

[0063] After the coefficient setting is completed, a period of observation will begin, and then the above judgments and adjustments will be made.

[0064] (2) Corrected trend coefficient Kb

[0065] According to the changing trend of the target parameter data in the continuous time period T, the adjustment coefficient Kb is set.

[0066] The model performs five periodic samplings of the indicator with a period of t, sorts and compares the sampled data, and if the five sampled data have an obvious upward trend, the coefficient Kb is set to 0.4; if the five sampled data have no obvious upward trend and fluctuate up and down, the coefficient Kb is set to 0;

[0067] (3) Corrected flow coefficient Kc

[0068] Calculate the real-time ratio of the influent flow rate of the current reaction tank to the designed scale flow rate, determine whether it is operating at full load, and set the adjustment coefficient Kc;

[0069] First, calculate the real-time ratio P of the influent flow rate of the current reaction tank to the designed scale flow rate;

[0070]

[0071] Where: Q t is the influent flow rate of the sedimentation tank at the current time; Q e is the designed scale flow rate of the water plant;

[0072] If 0.4 < P < 0.8 (t ≥ 15 min) within a continuous period T, then set the coefficient Kc = -0.3; if operating at full load, that is, P ≥ 1.0 (t ≥ 15 min) within a continuous period T, then set the coefficient Kc = 0.3;

[0073] In summary, the parameters of the model have been corrected.

[0074] S3. Calculate the amount of medicine to be added for treating unit mass of water at the next moment. The calculation formula is:

[0075] M k = M k-1 ×[(Ka + Kb + Kc)×R + 1]

[0076] Where:

[0077] M k is the amount of medicine to be added for treating unit mass of water at the next moment;

[0078] M k-1 is the amount of medicine to be added for treating unit mass of water at the previous moment;

[0079] R is the upper limit of the given change range;

[0080] Calculate the dosing flow rate F. The calculation formula is as follows:

[0081]

[0082] Where:

[0083] F is the dosing flow rate of alkali aluminum, with the unit of L / h;

[0084] f1 is the influent flow rate of the sedimentation tank, with the unit of m 3 / h;

[0085] M k is the amount of medicine to be added for treating unit mass of water, with the unit of mg / L;

[0086] ρ is the density of the solution in which the flocculant is dissolved, in kg / L;

[0087] λ is the concentration of the solution in which the flocculant is dissolved;

[0088] S4, judging whether the dosing flow rate value calculated in step S3 is greater than the current dosing flow rate, if yes, continue to judge whether the dosing pump put into operation is already running at the highest frequency, if yes, put the standby pump into operation, otherwise increase the working frequency of the dosing pump already put into operation;

[0089] Determine whether the dosing flow rate value calculated in step S3 is less than the current dosing flow rate. If so, continue to determine whether the dosing pumps in operation are already running at the lowest frequency. If so, stop one of the pumps and switch it to standby, otherwise reduce the operating frequency of the dosing pumps that have been put into operation; if the calculated value is equal to the current value, it is considered that there is no need to adjust the dosing pump, and return to step S1 after a certain delay.

[0090] The present invention also provides a precise alkali-aluminum dosing control system for raw water treatment, comprising: an inlet water online flow meter, an online turbidity monitoring instrument, a variable frequency dosing pump, a PLC control cabinet, and a host computer. The host computer executes the precise alkali-aluminum dosing control method for raw water treatment as described above, so as to obtain real-time data of the inlet water online flow meter and the turbidity online monitoring instrument through the PLC control cabinet, and transmit the processed data to the host computer for processing. The host computer sends a signal for adjusting the working frequency of the variable frequency dosing pump to the PLC control cabinet based on the data to adjust the flow rate of the alkali-aluminum added to the sedimentation tank.

[0091] The sedimentation reaction tank, as a link in the raw water sedimentation treatment, provides the function of water storage and static placement; the water inlet online flow meter and the turbidity online monitor constitute the data acquisition module, which collects the water inlet flow and raw water turbidity data in real time, and sends the data to the core controller PLC through the 485 serial port communication line; the function of the variable frequency dosing pump is to transport the pre-configured flocculant to the sedimentation reaction tank. The pump is a variable frequency pump that supports on-site and remote adjustment of the working frequency; the PLC control cabinet includes network devices such as data acquisition module, CPU, communication module, routing gateway, etc. The acquisition module is electrically connected to the controlled equipment, such as the variable frequency dosing pump, on one hand, and electrically connected to the CPU through the PLC backplane on the other hand. The CPU, as the core controller, runs the control program and is connected to the host computer through the network; the host computer runs the SCADA service and runs the front-end program that facilitates human-computer interaction.

[0092] The sedimentation reaction tank is set at the front end of the water treatment pipeline of the whole plant, and is directly connected to the water inlet pipeline or indirectly connected through the water distribution well. The process principle of the sedimentation reaction tank is as follows: the raw water flows into the sedimentation reaction tank through the water inlet pipeline, and is left to settle here. The sludge, sand, garbage, etc. in the water are naturally precipitated, and the remaining large suspended particles in the water cannot be naturally precipitated. Alkali aluminum reagents, i.e. flocculants, are added into the tank through the dosing pump to absorb impurities in the water, promote coagulation, and accelerate the sedimentation process.

[0093] PLC communicates with lower sensors to obtain real-time data, and forwards it to the upper computer for display and storage in the database. At the same time, PLC cleans and screens the original collected data according to the built-in model and control program, and then groups the valid data for periodic analysis to determine the turbidity of the water in the current pool and its changing trend, and calculates the amount of medicine required to treat the unit volume of water at the next moment. In addition, based on the operation of the water plant, it calculates how much the addition flow should be adjusted, and compares this calculated value with the current value to determine whether it is necessary to adjust the output of the variable frequency dosing pump, and then sends a command to increase or decrease the frequency.

[0094] The host computer is a SCADA server and database server, which is used to display the real-time value of the original data, the calibration value of the model parameters, the output value of the model calculation, the command decision automatically issued by the PLC to the controlled equipment, the alarm value of the controlled equipment and even the whole process, the economic operation and workload curve of the water plant, etc. For any decision of the PLC automatic control, the water plant operation and maintenance personnel can take over the control right, modify the model parameters or directly issue control commands to any controllable controlled equipment.

[0095] Specifically, the present invention is further described in detail with reference to the accompanying drawings and specific embodiments.

[0096] like Figure 1 As shown, the precise intelligent dosing system of alkali aluminum of the present invention includes a sedimentation tank, a PLC control cabinet, a SCADA server, a dosing pump, a water inlet pipe, an online water inlet monitor, and a turbidity monitor. The sedimentation tank is a pool where the raw water undergoes flocculation and sedimentation process, and is the first process of raw water treatment. It is connected to an inlet pipe and a dosing pipe, and is equipped with a turbidity monitor for collecting turbidity data of water in the pool; the online water inlet monitor is installed in the inlet pipe to collect inlet flow data; the PLC control cabinet contains PLC (process logic controller), power module, communication management machine and other equipment; the PLC is electrically connected to the controlled equipment, and is connected to the turbidity sensor and flow sensor through a 485 serial line to achieve remote control and communication. The PLC is connected to the SCADA server through a network cable, and the SCADA server runs the SCADA program.

[0097] The turbidity and flow sensors send the real-time raw water turbidity and inlet flow data to the PLC via serial communication. The PLC cleans the real-time collected data through the limiting filter method, removes abnormal and disturbance signals, and uses the cleaned data as the input of the model to analyze the change trend of the current data and correct the parameters of the calculation model. The output of the calculation model is the expected value of the unit consumption and the dosing flow in the current state. This expected value is compared with the actual value of the current unit consumption and the dosing flow. If the expected value is higher, the PLC sends a higher operating frequency to the inverter of the dosing pump, and if the expected value is lower, the PLC sends a lower operating frequency to the dosing pump. The automatic adjustment process of model calculation plus negative feedback is completed by the PLC's CPU.

[0098] The specific calculation method of the model is combined with Figure 2 Detailed description:

[0099] S1. According to the process control requirements, the target parameters are periodically sampled and then filtered by the limiting filter method, and then the valid data (Z1, Z2, Z3, ..., Z n ), hereinafter referred to as data;

[0100] S2. Correction of model parameters

[0101] (1) Determine whether the turbidity data after sedimentation for 40 consecutive minutes is within the preset range. If yes, set the threshold coefficient Ka = -0.3, otherwise set it to 0.3;

[0102] (2) Determine whether the data in 5 consecutive sampling periods within 10 minutes show an upward trend. If so, set the trend coefficient Kb = 0.4; otherwise, continue to determine whether the data in 5 consecutive sampling periods within 10 minutes show a downward trend. If so, set the trend coefficient Kb = -0.4; otherwise, it is considered that the data tends to be stable or fluctuates up and down, and there is no obvious trend, so the trend coefficient is set to 0;

[0103] (3) Determine whether the real-time ratio of the inlet flow rate to the maximum design flow rate of the water plant is greater than 0.4 within a time interval of not less than 15 minutes, and less than 0.8, then it is considered that the current water plant is not in full load working state, and the flow coefficient Kc is set to -0.3; if the ratio is greater than 1 for more than 15 minutes in a row, then it is considered that the current water plant is in full load operation state, and the flow coefficient Kc is set to 0.3;

[0104] S3. Calculate the dosage M required to treat a unit mass of water at the next moment k Here, the change range R is set to 5%, so that the adjustment range each time is within the controllable range and over-adjustment is avoided. Calculate the addition flow rate F.

[0105] S4. Determine whether the dosing flow rate calculated in step S3 is greater than the current dosing flow rate. If so, continue to determine whether the dosing pump in operation is already running at the highest frequency. If so, put the standby pump into operation, otherwise increase the operating frequency of the dosing pump that has been put into operation;

[0106] Determine whether the dosing flow rate calculated in step S3 is less than the current dosing flow rate. If so, continue to determine whether the dosing pumps in operation are already running at the lowest frequency. If so, stop one of the pumps and switch it to standby. Otherwise, reduce the operating frequency of the dosing pumps in operation. If the calculated value is equal to the current value, it is considered that there is no need to adjust the dosing pump, and return to step S1 after a certain delay.

[0107] Through the description of the above embodiments, it can be seen that the alkali-aluminum precise intelligent dosing system of the present invention has the advantages of good stability, high reliability, precise control, etc., can effectively improve water treatment efficiency, reduce energy consumption and resource waste, and has important practical value and application prospects.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for accurately dosing alkali aluminum for raw water treatment, characterized in that: Including real-time data acquisition, model building and model parameter correction, calculation of dosing flow and automatic control of dosing pump; S1. Real-time data collection: According to the process control requirements, the target parameters are periodically sampled and then filtered by the limiting filter method, and then the valid data Z1, Z2, Z3, ..., Z n ; S2. Model establishment and model parameter correction S21. Establish a universal calculation model applicable to the dosing system in the raw water treatment process. The model is used to analyze the changing trend of the monitoring data in the current period and calculate the dosing unit consumption and dosing flow required for the sedimentation tank. The input of the model includes the sampling value, upper and lower limits of the target parameters, and the flow ratio. S22. Model parameter correction (1) Correction threshold coefficient Ka According to whether the data in the continuous time period T is within the threshold range of the process requirements, the adjustment coefficient Ka is set; (2) Corrected trend coefficient Kb The model samples the indicators with a period of t, sorts and compares the sampled data, and adjusts the adjustment coefficient Kb according to the change trend of the data in the continuous time period T; (3) Corrected flow coefficient Kc Calculate the real-time ratio of the current inlet flow rate of the reaction tank to the design scale flow rate, determine whether it is running at full load, and set the adjustment coefficient Kc; S3. Calculate the dosage required to treat a unit mass of water at the next moment. The calculation formula is: M k =M k-1 ×[(Ka+Kb+Kc)×R+1] in: M k The dosage required to treat a unit mass of water at the next moment; M k-1 The dosage required to treat a unit mass of water at the last moment; R is the upper limit of the given change range; Calculate the addition flow rate F, the calculation formula is as follows: in: F is the alkali aluminum addition flow rate, in L / h; f1 is the inflow flow rate of the sedimentation tank, in m 3 / h; M k The dosage required to treat a unit mass of water, in mg / L; ρ is the density of the solution in which the flocculant is dissolved, in kg / L; λ is the concentration of the solution in which the flocculant is dissolved; S4, judging whether the dosing flow rate value calculated in step S3 is greater than the current dosing flow rate, if yes, continue to judge whether the dosing pump put into operation is already running at the highest frequency, if yes, put the standby pump into operation, otherwise increase the working frequency of the dosing pump already put into operation; Determine whether the dosing flow rate value calculated in step S3 is less than the current dosing flow rate. If so, continue to determine whether the dosing pumps in operation are already running at the lowest frequency. If so, stop one of the pumps and switch it to standby, otherwise reduce the operating frequency of the dosing pumps that have been put into operation; if the calculated value is equal to the current value, it is considered that there is no need to adjust the dosing pump, and return to step S1 after a certain delay.

2. A precise alkali-aluminum dosing control system for raw water treatment, comprising: An inlet water online flow meter, an online turbidity monitoring instrument, a variable frequency dosing pump, a PLC control cabinet, and a host computer, characterized in that: the host computer executes the precise alkali-aluminum dosing control method for raw water treatment as described in claim 1, so as to obtain real-time data of the inlet water online flow meter and the turbidity online monitoring instrument through the PLC control cabinet, and transmit the processed data to the host computer for processing. According to the data, the host computer sends a signal for adjusting the working frequency of the variable frequency dosing pump to the PLC control cabinet to adjust the flow rate of the alkali-aluminum added to the sedimentation tank.

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