Seasonal variation in the physicochemical and bacteriological qualities of well water in two sub-divisions of Moundou city (Southern Chad, Central Africa)

This study were carried out from May 2019 to July 2020 with the aimed of evaluating the physicochemical and bacteriological quality of well water in the City of Moundou (Chad). The physicochemical analysis showed that, the water from wells in the two sub-divisions were of very poor quality with an average concentration in Suspended Solids (SS) 30.73 ± 2 1.72 mg.L-1, a Turbidity of 11.10 ± 13.34 FTU, the Electrical Conductivity of 1625.9 ± 1398.6, a Total hardness of 1693.1 ± 1198.2 mg.L-1, Biochemical Oxygen Demand (BOD5) of 167.67 ± 60, 28 mg.L-1, the Chemical Oxygen Demand (COD) 605.93 ± 259.98 mg.L-1 and organic matter 3.75 ± 2.40 mg.L-1. The contamination rate (% non-compliance) of the water points indicates that, during the rainy season the wells were moderately contaminated. Salmonella spp and Escherichia coli induced 29% and 14% respectively, of samples which did not comply with the WHO evaluation criteria (0 germ/mL). As for Total Coliforms and Fecal Coliforms, they were 93% non-compliant each time in the well water samples analyzed. During the dry season, the wells were heavily contaminated with Salmonella spp, Escherichia coli, Total Coliforms and Fecal Coliforms induced approximately 100% of samples were not conform to the criteria of the WHO (0 germ/mL). These waters are therefore not safe for direct consumption without treatment.