Conceptual Framework for Integrating Real-Time Control and Source Control Solutions for CSO Frequency Control

Abstract

Combined sewer overflows (CSO) are associated with water quality degradation and health risks, but limited knowledge exists on the optimal solutions applicable to reach maximal overflow frequency targets as specified by some regulatory agencies. This study assesses the potential benefit of integrating source control with real-time control solutions based on hydrological/hydraulic modelling of urban catchments of the Province of Québec (Canada). Firstly, modelling procedures for volume sizing of CSO solutions are improved by determining the proper rainfall input among the three most common types of rainfall data (continuous simulation, historical rainstorms and IDF-derived storms) excluding winter months in the analysis to be aligned with Quebec legislation. Secondly, a methodological framework is developed to integrate source control and optimal real-time control solutions based on a cost-efficiency performance objective. Thirdly, two optimization software are coupled to iteratively solve for the best flow management strategy according to physical and operating constraints; iPOP for source control design and CSoft for dynamic control. Preliminary results showed that simulation of continuous rainfall series results in the most accurate volume estimations for sizing CSO solutions and IDF-derived design storms could serve as input data for initial optimization runs. Based on the determined appropriate rainfall data, source control optimization showed considerable solutions implementation cost reduction for acceptable runoff reduction. Future work includes refining the integrated solution framework and comparative analysis of modelling results under optimal implementation of source control and real-time control solutions.