147 - Robust Booster Disinfection Scheduling Using Non-uniform Mixing Water Quality Models

In the realm of practical water distribution systems (WDS), uncertainties in hydraulic and water quality modeling affect management of WDS making it a multifaceted challenge. Furthermore, the incorporation of water quality considerations into WDS design and management has become paramount, necessitating the use of precise water quality models. The conventional water quality models employed in drinking WDS have faced inaccuracy due to their underlying assumption of instantaneous and complete mixing at junctions. To address this limitation, recent models such as EPANET-IMX (Incomplete Mixing Extension) and AZRED have emerged, incorporating empirical equations to model the nuances of non-uniform mixing. These advancements offer improved accuracy for water quality analysis within WDS. However, the presence of uncertainty in disinfectant reaction rates presents a formidable obstacle in achieving optimal water quality management. Within such systems, determining the scheduling of booster disinfectant dosages is a challenge. In response, this study seeks to determine the optimal dosage schedule for booster disinfectants while accounting for fluctuations in bulk reaction rate coefficients and acknowledging non‑uniform mixing at junctions. To tackle this uncertain optimization problem, robust optimization principles are employed. The study applies these principles to a small-scale network as an illustrative example, showcasing robust optimal schedules. Three distinct water quality models, namely EPANET, EPANET-IMX, and AZRED, are utilized for water quality simulations. The resulting optimal schedules are compared and analyzed across all three models. It was observed that considering the non‑uniform mixing varied the optimal booster dosage by about 10%. The findings emphasized the growing importance of considering non-uniform mixing in both water quality analysis and optimization endeavors.