Global optimal control for regional sewer systems

In order to control combined system overflow （CSO） pollution of regional sewer systems in Shanghai, a global optimal control （GOC） is presented in this study. The GOC is based on the analysis of current situation and can maximize the utilization of the free storage of each sub systems and decrease the frequencies and durations of CSOs and flooding. A representative regional sewer system, which is located in the northwest of Shanghai and composed of sub systems of Zhenguang, Zhenru and Tongchuan, was taken as an example to dem- onstrate the efficiency of GOC with hydraulic model simulation test in the two representative scenarios （ Scenario Ⅰ and Ⅱ）. The results indicated that a great improvement in CSO emission is obtained by using the GOC in the two scenarios, and the CSO volume of three sub systems, Zhenru, Tongchuan and Zhenguang decreases to about 37.0% , 38. 3% and 35.7% in Scenario Ⅰ and 47.5%, 51.8% and 63.5% in Scenario Ⅱ respectively.