Application of stormwater mass–volume curve prediction for water quality-based real-time control in sewer systems

Reducing emitted pollutant loads via combined sewer overflow (CSO) structures is important to protect receiving water bodies. This study implements two real-time control (RTC) strategies: water quality-based RTC (QBR) using mass–volume (MV) curves versus simple hydraulics-based RTC (HBR) on a small sewer network and then uses the performance of HBR as a reference to evaluate the performance of QBR. The control strategies are tested on 31 storm events with CSOs over a two-year period. Compared to HBR, QBR delivers CSO load reduction for more than one-third of the storm events, with reduction values from 3% to 43%. By characterizing the MV curves, it is possible to sort the storm events into three groups having different probabilities of the benefit of QBR. Sensitivity analysis results also indicate the significant impact of control time interval and retention tank volume towards the efficiency of QBR.