Multi-objective optimization of hydrant flushing in a water distribution system using a fast hybrid technique

Area of Science:

• Environmental Engineering
• Water Resource Management
• Risk Analysis

Background:

• Urban water distribution systems (WDSs) require robust emergency plans for contamination events.
• Existing methods face challenges with uncertainty and computational runtime.

Purpose of the Study:

• To develop a risk-based simulation-optimization framework for optimal contaminant flushing hydrant placement in WDSs.
• To address uncertainties in contamination scenarios and decision-maker conflicts.

Main Methods:

• Integrated EPANET-NSGA-III (simulation-optimization) and GMCR (conflict modeling) framework.
• Conditional Value-at-Risk (CVaR) for risk-based objectives and a hybrid grouping-parallel simulation technique.
• Evaluated on a real-world WDS in Lamerd, Iran.

Main Results:

• Achieved an optimal compromise solution for hydrant placement, reducing risks by 35-61.3% and recovery time by 14.4-60.2%.
• Reduced model runtime by nearly 80%, enabling online simulation-optimization.
• Identified a cost-effective strategy using less than half of potential hydrants.

Conclusions:

• The proposed framework provides a viable and efficient solution for WDS contamination management.
• It enhances WDS resilience against contamination events while optimizing resource allocation.
• The study demonstrates practical applicability for safeguarding urban water systems.