System-Wide Real Time Control Strategies for Overflow Volume Reduction - Extrapolating Annual Performance Indicators

Advanced real time control strategies of sewer networks can provide a significant contribution to the reduction of overflow volumes. Before full-scale implementation, these strategies need to be tested over long-time periods to calculate key performance indicators, such as yearly reduction in overflow volumes. This evaluation is often hindered by lack of sufficiently long data series. A new method was proposed to extrapolate yearly CSO reduction performance by using simulations of a limited number of CSO events. This article evaluates the precision of this extrapolation method by testing its precision in estimating CSO volumes yearly reduction for a synthetic example and a case study in Copenhagen (Denmark). The results showed a minor difference (2-3%) in the estimated CSO reduction for the synthetic example. However, the method overestimated the yearly CSO reduction for the real case study, mainly due to yearly variation and to nonlinearity in the performance of control strategies. These preliminary results suggested that the extrapolation method converges with a lower number of CSO events compared to a simple sum of CSO volumes. Both the methods are thus suggested to obtain a more precise estimation of the yearly performance of advanced real time control strategies.