Département de Gestion des Ressources Naturelles et Systèmes de Productions (GRN-SP), Centre National de la Recherche Scientifique et Technologique, Institut de l’Environnement et de Recherches Agricoles (CNRST/INERA), Laboratoire Sol - Eau - Plante, 01 BP 476 Ouagadougou 01, Burkina Faso
In Burkina Faso, Water resources are threatened today by pollution from domestic waste, industrial and agricultural discharges without adequate treatment. This pollution is the main cause of degradation of water quality. The objective of this study is to evaluate the physicochemical quality of the water in the market garden site of Kossodo watered with sewage sludge from the city of Ouagadougou industries. Indeed, seven (7) wastewater samples collected over a 90 days period at the site where a Water Treatment Plant (WTP) was installed were analysed in the laboratory. The parameters were pH, EC, Ca2+, Mg2+, Na+, K+, Cl-, SO42-, NH4+, NO3-, HCO3-, CO32- , BOD5, SM and COD. The analytical data was compared to WHO standards. The Results show that the concentrations of the chemical elements are very high in the wastewater, but hardly exceed the levels recommended by the standards for agro-pastoral needs. Electrical conductivity indicates that 57% of the samples analysed are not saline. Phosphorus and potassium concentrations are low. There is a strong mineralization resulting from industrial or domestic pollution. The physicochemical characterization of the raw wastewater revealed that this liquid discharge is very heavy in organic matter in term of COD (Avg.= 341.52 mg/L), in BDO5 (Avg.= 260 mg/L), in Suspend Matter (Avg.= 307.6 mg/L) and mineral matter expressed in terms of chlorides (Avg.= 75.968 mg/L), electric conductivity (Avg.= 580.24 µs/cm) and alkalinity expressed as CaCO3 (Avg.= 220.70 mg/L) with a pH of 7.5 (±0.3). The average levels of nitrates and orthophosphates respectively of the order of 33.11 mg/L and 86.74 mg/L. Over the entire sampled site, most of the wastewater analysed is suitable for agriculture.