Assessment of Organic Pollutant Index and Biodegradability Index in Determining River Pollution Load

Abstract The Kupang River, a major watershed in Batang and Pekalongan, spans 53 kilometres and has been experiencing significant water quality degradation. Notably, the river’s colour changes to black and emits foul odours, especially during the dry season. This deterioration is attributed to extensive batik industries and residential areas along its banks, leading to severe pollution. This study aims to identify the primary factors contributing to the pollution of the Kupang River from 2021 to 2024 using organic pollutant and biodegradability index. Pollution loads were calculated across five monitoring segments to determine the river’s waste disposal capacity. The findings reveal potential agricultural pollution in the upstream segment, indicated by slow-biodegradable and non-biodegradable degradation. Thus, the downstream segment shows high levels of organic pollution, with degradation ranging from moderate to very strong polluted levels. Pollution load calculations indicate that Kupang River can accommodate pollution loads for TSS up to 30294,49 kg/day, BOD up to 763,03 kg/day, and COD up to 5935,96 kg/day. However, BOD’s low pollution load capacity should be a serious concern, highlighting severe contamination issues that necessitate immediate attention and remediation.