The Optimization Of Dosage Control System In Water Plants

Water supply is an important industry related to the national economy and people’s livelihood as the quality of water from waterworks directly affects the people’s living standards. With the sustained development of economy and people’s living standards, a higher requirement is put forward for the city water supply. That is to ensure not only an adequate water supply but also a higher water quality. Autonomic control of water treatment is one of the keys to guarantee the water quality. Its main difficulty concerns about how to control the coagulant dosing process. Nowadays many waterworks in our country mainly adopt two ways for the dosing process: one is the artificial control based on the human experience while the other is the autonomic control based on the PID control algorithms. However both of them are not very good in the regard of their control effects. The problems arise from the large fluctuation of water turbidity,serious waste of coagulant and etc. How to optimize the dosing system to achieve the optimum amount of coagulant which adjusts the dosage to the raw water flow and the change of water quality is an urgent problem to be solved in the water treatment industry.According to the practical situation of Dalian Huayuankou emergency water supply project,we make a general design for the automatic control system at this waterworks. For the existing problems in dosing control system, we propose a feedforward-feedback optimal control framework in which a dynamic integration separation PID algorithm is firstly applied in the feedback control of water turbidity and implemented by PLC. The main works of this thesis are as follows:(1) Design the waterworks’ autonomic control system structure based on distributed control after the further analysis of water treatment(2) Improve the algorithms of dosing control. Design a feedforward-feedback optimal control framework. Propose a dynamic integration separation PID algorithm to achieve a new way of autonomic dosing control.(3) Implement the project of optimal dosing control. It mainly includes two parts: hardware and software design. For the latter it incorporates: automatic dosing mixing, automatic switching of bottle and dosing frequency control.(4) Design and implement of computer monitor system. PC software uses the Kingview6.53by Beijing Asia Control Company. The PC configuration software enables the operators have a comprehensive monitoring at the site. (5) System operation and debugging. Debug the running system of dosing system and provide a data report of actual operation at the waterworks. Production data shows that the water turbidity can be stabilized at0.5NTU and the utilization of a coagulant after system optimum is effectively improved.