Development of operational real-time control strategies for reduction of combined sewer overflows

Abstract

Real-time control (RTC) is an efficient way to reduce CSO and considerably cheaper than increasing wastewater storage volume by construction of basins. Despite this, wastewater operators are reluctant to implement such systems and enhanced methods for application of RTC are needed. Rule-based real-time control is considered the simplest control method and while being widely applied there are plenty of experience from previous cases to benefit from. This study aims at identifying rule-based RTC applications that are generic and well documented. Identified rule-based control strategies have undergone a translation process preparing them for easier implementation on new systems. Control strategies were implemented and tested on a combined sewer system in Bistrup, Denmark (9.000 PE), and followingly evaluated with respect to CSO reducing abilities on four years of historic rainfall data. The study found that many documented applications exist, however, at detail levels insufficient for further implementation. A handful of control strategies were successfully translated and tested. However, they led to insignificant CSO reductions of 2-3% and behaved very similar in terms of performance and function. Improvements to the control-related structure of the system and subsequently testing with one control strategy yielded much higher CSO reductions. Therefore, it was also concluded that successful applications of rule-based RTC are more dependent on the system that the control strategies applied.