Assessment of the Impact of Palm Oil Mill Effluent on Water Quality of The Oko-Oko River, Indonesia

Abstract

Palm oil mill effluent (POME) is one of the primary sources of water pollution in tropical watersheds, especially in areas where waste treatment is not yet optimal. This study aims to evaluate the impact of reducing POME pollutant loads on water quality in the Oko-Oko River in Kolaka District, using parameters such as dissolved oxygen (DO), biological oxygen demand (BOD), and chemical oxygen demand (COD). The method employed uses the QUAL2Kw water quality model, which has been calibrated and validated. Three pollution load reduction scenarios—baseline/no reduction (Sim1), 30% POME load reduction (Sim2), and 70% POME load reduction (Sim3)—were analyzed to assess changes in DO concentration, BOD, and COD at four monitoring stations. The accuracy of calibration and validation is tested based on the calculation of Root Mean Square Error (RMSE) and Nash-Sutcliffe Efficiency (NSE) coefficient functions. Model validation showed excellent agreement between simulation results and observational data, with NSE values for BOD = 0.832 (RMSE = 0.584), DO = 0.962 (RMSE = 0.655), and COD = 0.816 (RMSE = 2.548). Simulation results indicate a 70% reduction in POME load could increase DO concentration in the downstream section from 6.09 to 6.16 mg.L^-1, while BOD and COD would decrease by 7.2% and 5.4%, respectively. These results support the effectiveness of the integrated anaerobic-aerobic filtration system in reducing pollutant loads and ensuring water quality meets Class II national water quality standards.