Suivi de la qualité physico-chimique et bactériologique des eaux des cours d’eau de Ngaoundéré, au Cameroun

Dans le souci d’evaluer l’influence possible des activites anthropiques sur les eaux de surface a Ngaoundere, des analyses des parametres physico-chimiques et bacteriologiques indicateurs de pollution ont ete effectuees sur dix sept (17) points d’echantillonnage retenus en fonction de leur sollicitation par les populations et leur exposition aux sources probables de pollution. Les parametres physico-chimiques (temperature, pH, conductivite, turbidite, matiere organique en suspension, oxydabilite au permanganate de potassium, fer, bicarbonates, nitrates, phosphates et ammonium) et bacteriologiques (streptocoques fecaux et vibrions) ont ete analyses et compares aux normes internationales. Les resultats montrent des fortes concentrations en matiere organique (9,30 a 10,56 mgO 2 /L), Fer (1,69 a 5,57 mg/L), Phosphates (1,73 a 3,09 mg/L), ammonium (1,78 a 2,19 mg/L) et une de turbidite 63,32 a 64,05 NTU dans ces eaux. En plus ces eaux hebergent d’importantes communautes microbiennes parmi lesquelles les streptocoques fecaux et les vibrions. Les teneurs de ces polluants different d’un point a un autre et selon la periode de prelevement. Une approche statistique multi-variee des resultats montre que l’activite anthropique reste la source majeure des rejets polluants dans les eaux. Mots-cles: pollution, physico-chimie, bacteriologie, eaux de surface, Ngaoundere, Cameroun. Survey of physico-chemical and bacteriological quality of water along the Ngaoundere stream (Cameroon) To evaluate the possible influence of human activities and nature on Ngaoundere stream, some physicochemical and bacteriological pollution indicators were analyses carried out on 17 sites selected on the basis of their probable exposure to pollution. Physicochemical parameters (temperature, pH, conductivity, turbidity, suspended matter, organic matter, iron, bicarbonates, nitrogen, phosphates and ammonium) and bacteriological parameters (fecal streptococcus and vibrio) were determined and compared to international standards.  Results obtained showed a high concentration in organic matter (9.30 to 10.56 mgO 2 /L), iron (1.69 to 5.57 mg/L), phosphates (1.73 to 3.09 mg/L), ammonium (1.78 to 2.19 mg/L) and turbidity of 63.32 to 64.05 NTU. The presence of high quantities of test micro-organisms was noted in these water samples, that is fecal streptococcus and vibrio. The levels of these pollutants in the different water samples varied from one site to another and with sampling period. A multivariate statistical approach demonstrated that human activities remained the major sources of pollutants in surface water. Keywords: pollution, physicochemical, bacteriological, surface water, Ngaoundere, Cameroon.