Reform Project Of Dosing Automatic Control System In A Water Purification Plant

At present,there are some problems about high consumption of coagulants and chlorine agents in many water purification plants in China.Turbidity and residual chlorine of deliver water can not reach the expected value.Coagulation and chlorination are key links in the processes of water purification plant,the dosage directly affects the efficiency of water treatment and the quality of deliver water,and even threatens human health.However,coagulation and chlorination are complex physical,chemical and biological processes,which there are many disturbance factors,and it has the characteristics of long delay and nonlinear change.Nowadays,there are still many water purification plants are adding coagulants and chlorine agents with the water quality was measured by experience,and the dosage was added by manual control.this dosing method has been difficult to deal with the large fluctuations of original water quality in the water purification plant.Combined with the actual situation of a water purification plant in Changchun City,analysis the operation condition of the water purification plant before the reformation and discusses the necessity about reformation of dosing system.the water treatment is difficult due to low temperature and low turbidity of raw water and aging of equipment.Dosing system has been difficult to make the water turbidity to meet the standard requirements.Chlorination of the chlorine system is also difficult to achieve the desired value.The chlorine control device in a paralyzed state,which can not guarantee the safe operation of chlorine system.Automatic control transformation of water purification plant dosing system is imminent.Dosing system tracks and records the signals in accordance with the turbidity of the deliver water and the water quantity of the raw water through the on-line instrument.The PID compound operation is carried out according to the operation process,parameters and mathematical model.The operation result is transmitted to the metering pump to realize automatic closed-loop regulation of dosing system.The pre chlorination is added according to the influent flow ratio of the sedimentation tank,and the post chlorination is added according to the feedback of the residual chlorine.PLC control the chlorination machine according to the influent flow rate and the set dosing ratio,so as to realize the automatic control of chlorine dosing.The average consumption of coagulant was reduced by nearly 34%,the average value of turbidity decreased by 0.17 NTU every month,and the qualified rate of the deliver water was increased by nearly 17% after the dosing system was reformed.Consumption of coagulants is less and the turbidity of deliver is more stable to compare with before reformation,The average consumption of chlorine agents was reduced by 0.41mg/L,nearly 34%,and the total number of bacteria in the end of the clean water pool was reduced by nearly 54% after the chlorination system was reformed.The consumption of chlorine agents is less and residual chlorine in deliver water is more stable.The automatic control of chlorine system is more accurate than the manual control of chlorine system.The automatic control of chlorine system have a small error to ensure that the amount of chlorine can meet the expected value of the drinking water requirements,and it with significant social benefits.The reformed chlorine automatic control system can accurately control the amount of chlorine according to the influent and effluent conditions,which has high accuracy and high flexibility,and basically overcomes the influence of water fluctuation on chlorine dosing.The improved chlorine leakage device can effectively control the occurrence of chlorine leakage accident,and effectively improve the safety performance of the water treatment plant.The paper puts forward the problems of the dosing system of the water purification plant and the necessity of the system reformation,and expounds the relevant technical principles of the system reformation.The paper compares and analyzes the operation status as well as the social and econerzomic benefits of the water purification plant with the before and the after reformation.It can provide reference for the similar raw water quality and operation profile of the water purification plant pharmacy dosing system reformation and production operation,and can provide the scientific basis for the north area water treatment.