Water quality and pollution load capacity of the Rungan River in Tangkiling, Palangka Raya, Indonesia

Abstract

This study assessed water quality and pollution-load capacity in the Rungan River around Tangkiling, Palangka Raya, Central Kalimantan, Indonesia. Water was sampled at four purposively selected stations in June 2025, with field measurements and laboratory analyses conducted on three occasions at seven-day intervals. Temperature, current velocity, depth, total suspended solids (TSS), total dissolved solids (TDS), pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), phosphate, and nitrate were examined. Results were compared with the water-quality classes specified in Indonesian Government Regulation No. 22/2021. Mean temperature was 26–28 °C, TSS was 109–127 mg/L, TDS was 9.6–10.1 mg/L, pH was 4.1–4.6, DO was 2.8–3.2 mg/L, and BOD was 4.0–8.4 mg/L. TSS exceeded the reported limits for Classes 1–3, while DO was below the requirements for Classes 1–2. BOD was elevated at Stations I, II, and IV relative to the reported Class 3 criterion; Station III had the lowest mean BOD. The acidic pH was attributed by the original study to the river’s peat-swamp setting, although this interpretation requires consideration of local baseline conditions. The manuscript’s load-capacity calculations indicated negative capacity for TSS and BOD, but positive capacity for TDS, phosphate, and nitrate. Several inconsistencies in the source calculations and units prevent the reported pollution-load values from being treated as validated estimates. Overall, the results indicate that suspended solids and oxygen-demand conditions warrant priority monitoring and source-control measures.