Assessment of the Pollutant Load of the Logone River Waters in the City of Moundou, Southern Chad

Abstract

The discharge of untreated industrial effluents into the Logone River poses serious risks to aquatic ecosystems and public health in Moundou, southern Chad. This study assessed the physicochemical quality of the Logone River at two monitoring stations one upstream and one downstream of the city during the dry season (May 2024) and the rainy season (July 2024). In situ measurements included pH, temperature, electrical conductivity (EC), and dissolved oxygen (DO). Laboratory analyses encompassed chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), nitrates (NO₃⁻), phosphates (PO₄³⁻), sulfates (SO₄²⁻), and heavy metals (Cu, Cd, Pb, Zn, Cr, Fe) using spectrophotometric and atomic absorption methods. Results were compared against World Health Organization (WHO, 2017) guidelines. Several parameters exceeded permissible thresholds: BOD₅ (198 mg/L), COD (897 mg/L), NO₃⁻ (10.6 mg/L), PO₄³⁻ (29.4 mg/L), Fe (4.65 mg/L), Zn (1.06 mg/L), Pb (0.037 mg/L), Cu (0.29 mg/L), and Cr (0.54 mg/L). The findings confirm that untreated industrial effluents from Brasseries du Tchad (BDT) and Cotontchad significantly contribute to organic and metallic contamination of the Logone River. Mandatory installation of wastewater treatment units is strongly recommended for all industrial facilities operating in the Moundou area.