The study looked at how leachate from a landfill in Indonesia affects the water quality of Pesanggrahan River. Leachate is a liquid that forms when waste breaks down. Samples were taken from the landfill and the river during the rainy season. The results showed that the leachate had high levels of pollutants like BOD, COD, and TN. The treatment plant did not fully remove these pollutants before releasing the leachate. The river downstream from the landfill had lower levels of dissolved oxygen compared to upstream, indicating pollution from the leachate.