ABSTRAK

Sungai Balangan dimanfaatkan untuk kebutuhan domestik, pertanian, perikanan, dan aktivitas ekonomi lainnya, sehingga kualitas airnya perlu dipantau secara berkala. Penelitian ini bertujuan mengevaluasi kondisi fisika-kimia air Sungai Balangan dan menetapkan status mutunya dengan metode Indeks Pencemaran. Sampel air dikumpulkan melalui grab sampling pada stasiun yang mewakili bagian hulu, tengah, dan hilir, masing-masing dalam tiga waktu pengamatan pada Januari–Februari 2026. Suhu, pH, dan dissolved oxygen (DO) diukur secara in situ, sedangkan total padatan tersuspensi (TSS), biochemical oxygen demand (BOD), dan chemical oxygen demand (COD) dianalisis di laboratorium. Hasil menunjukkan suhu 27,7–28,7 °C, pH 6,20–7,51, DO 6,2–7,3 mg/L, TSS 10–60 mg/L, BOD 20,66–24,33 mg/L, dan COD 41,47–46,72 mg/L. Nilai pH dan DO memenuhi baku mutu air sungai Kelas II, sementara satu pengamatan TSS melampaui 50 mg/L. Seluruh nilai BOD dan COD melampaui baku mutu, yang menunjukkan tekanan bahan organik dan senyawa teroksidasi di perairan. Nilai Indeks Pencemaran sebesar 5,2–5,6 menempatkan seluruh stasiun pada kategori tercemar sedang. Pengurangan masukan limbah domestik, pengendalian limpasan, serta pemantauan kualitas air yang konsisten diperlukan untuk mencegah penurunan mutu perairan lebih lanjut.

Kata kunci: BOD; COD; Indeks Pencemaran; kualitas air; Sungai Balangan

ABSTRACT

The Balangan River supports domestic, agricultural, fisheries, and other economic activities; therefore, its water quality requires regular assessment. This study evaluated the river’s physicochemical conditions and determined its water quality status using the Pollution Index method. Water samples were collected by grab sampling at three stations representing the upstream, middle, and downstream reaches during three observation periods in January–February 2026. Temperature, pH, and dissolved oxygen (DO) were measured in situ, whereas total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were analysed in the laboratory. The measured ranges were 27.7–28.7 °C for temperature, 6.20–7.51 for pH, 6.2–7.3 mg/L for DO, 10–60 mg/L for TSS, 20.66–24.33 mg/L for BOD, and 41.47–46.72 mg/L for COD. The pH and DO values complied with the Indonesian Class II river-water standards, while one TSS observation exceeded 50 mg/L. All BOD and COD values exceeded the permissible limits, indicating substantial pressure from organic matter and chemically oxidisable compounds. Pollution Index values of 5.2–5.6 classified all stations as moderately polluted. Controlling domestic wastewater inputs, reducing runoff, and conducting consistent water-quality monitoring are necessary to prevent further deterioration.

Keywords: Balangan River; BOD; COD; Pollution Index; water quality