Method and system for controlling coagulant dosing through on-line prediction of turbidity after flocculation water sedimentation

The invention relates to a method and a system for controlling coagulant dosing through on-line prediction of turbidity after flocculation water sedimentation. The method comprises the following steps of: making raw water enter a flocculation tank to mix, react and flocculate with the added coagulant so as to generate a flocculating substance; collecting the flocculation water in real time through a sensor for measuring the turbidity under the water at the tail end of the flocculation tank; sedimenting in the sensor in the given sedimentation time, and measuring the turbidity; comparing the measured value with the set value; and after the difference is subjected to PID operation, obtaining the needed dosing ratio, and multiplying the dosing ratio with the water inlet flow to obtain the dosing, converting the dosing into a standard current output signal to control the dosing of a dosing pump, and dosing the coagulant on line. The system consists of the flocculation tank, a sedimentation tank, the dosing pump, a coagulation tank, a microprocessor and a sensor 5 which is specially designed for measuring the turbidity. Due to adoption of the sensor for measuring the turbidity, the turbidity after flocculation water sedimentation can be accurately measured on line without being disturbed by other factors. Therefore, the on-line coagulant dosing can be accurately controlled, the coagulant dosing is reduced, the water purification quality is improved, and the water purification cost is lowered.