From Nominal Effluent to Deliverable Reclaimed Water: A Constraint-Based Framework for Diagnosing Operational Bottlenecks in Reclaimed-Water Service Delivery

Existing reclaimed-water planning approaches often evaluate potential supply using aggregate capacity-demand comparisons, although actual service depends on interacting source, operating, storage, loading, transfer and demand constraints. This study develops a constraint-based diagnostic framework for identifying the operational bottleneck that governs deliverable reclaimed-water service and for screening interventions under compound disruptions. The framework combines hourly state tracking with single- and multi-constraint stress testing and evaluates service ratio, reliability, storage exposure, abstraction curtailment, failure duration, bottleneck identity and intervention recovery. It is demonstrated using a planned system serving 148 urban-greening sites in Jeddah, Saudi Arabia, with a reconstructed annual irrigation demand of 774,813.35 m³. Under the design-stage parameterisation, annual service was 76.08%, compared with 76.05% from monthly capacity accounting. Thus, finer temporal resolution changed aggregate annual volume little under smooth demand but revealed operational states hidden by aggregation, including prolonged zero-storage exposure and abstraction curtailment. Compound source and operating constraints reduced annual service to 27.48%. Negative interaction metrics reflected bottleneck masking and lower-bound saturation rather than beneficial interaction. Intervention tests showed that added capacity at non-binding downstream stages produced little recovery when source availability or operating time governed throughput, whereas demand reduction and restoration of operating hours generated larger gains. The framework therefore shifts planning from nominal capacity accounting toward bottleneck-based service diagnosis. Numerical thresholds remain case specific; external empirical generalizability is not demonstrated, but the analytical structure provides a reproducible basis for identifying binding constraints and prioritizing further monitoring or intervention in comparable sequential delivery systems.