Dynamic Simulation of Industrial Shock-Load Impacts on a Domestic-Design Wastewater Treatment Plant: A GPS-X Case Study of the Jenin Industrial Free Zone, Palestine

The Jenin Industrial Free Zone Wastewater Treatment Plant (JIFZ-WWTP), an extended-aeration activated-sludge facility designed for domestic sewage, is required to serve an industrial catchment where unregulated effluents may enter without pretreatment. Because the plant was not yet operational, this study assessed its likely performance and shock-load vulnerability through dynamic simulation in GPS-X (v8.5, ASM1-based MANTIS), using a model calibrated on 728 laboratory measurements from a comparable operating plant (Jericho WWTP) and adapted to Jenin-specific conditions—an explicit methodological limitation. Under optimized steady state (RAS 460 m3/day, WAS 60 m3/day, capacity 1000 m3/day), the model indicated high simulated removals of TSS (95%), COD (90%) and cBOD5 (94%) but limited total-nitrogen removal (34%); simulated effluent COD (109 mg/L) marginally exceeded the Class C reuse target. A 1000 m3/day untreated industrial shock load over ten days drove near-complete nitrification failure, secondary-clarifier sludge washout and severe effluent exceedances (COD ≈ 8000 mg/L). Monte Carlo analysis showed that only 33% of influent scenarios meet the COD and cBOD5 limits simultaneously. Increasing the waste-activated-sludge rate was the most effective simulated recovery measure. These results, which require field validation once the plant is commissioned, indicate insufficient buffering against high-strength industrial inputs and support mandatory source pretreatment, continuous influent monitoring with early warning, and an anoxic stage with external carbon dosing.