Application of water quality modelling for effluent permit policy in the Cileungsi River, Bogor Regency, West Java Province

Effluent discharges from domestic and industrial sources have significantly deteriorated the water quality of the Cileungsi River. This study aims to calculate the allocation of water pollution load based on the capacity of water pollution load using a water quality model approach with the Qual2Kw software. The QUAL2K model was used to simulate the impact of pollutant loads on key water quality parameters, including biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS). Simulation results revealed that the existing BOD load was 4.480,37 kg/day, exceeding the allowable limit of 1,012.43 kg/day, based on Class II water quality standards. For COD, the current load was 28,196.76 kg/day, surpassing the acceptable load of 9,169.16 kg/day. In contrast, the TSS load was 3,765.38 kg/day, which remains below the maximum threshold of 5,245.69 kg/day. The model was calibrated and validated using field data collected from selected segments of the river. Validation results indicate that the model reliably predicts BOD and COD concentrations but shows limited accuracy for TSS estimation. Despite this limitation, the model effectively demonstrates the river’s pollutant carrying capacity under different discharge scenarios and helps identify acceptable effluent limits in compliance with national water quality regulations. This study underscores the critical role of integrating scientific modelling into environmental policymaking. It enables more precise, adaptive, and environmentally sound effluent management decisions. These findings serve as a valuable reference for the local government and environmental institutions in their efforts to improve river water quality through an evidence-based approach.