Quality and Chlorine Demand of Private Raw Borehole Water in the City of Kara, Togo

The reliance on borehole water necessitates a thorough understanding of its quality. Due to water shortage, many households in the city of Kara use water from boreholes directly supplied untreated in the dry and wet seasons. Therefore, this work aimed to investigate the chlorine demand of raw water from private boreholes and perform a spatiotemporal evaluation of the water quality in the city of Kara, Togo. Two sampling campaigns spread over dry (DS) and rainy (RS) seasons in April and August 2023, were carried out to capture seasonal and spatial differences across various boreholes (n=32) in the study area. The physicochemical parameters and germ indicators of fecal contamination were assessed via the standardized method (AFNOR) and WHO Guidelines for Drinking Water Quality (GDWQ). The correlation matrix analysis revealed a complex effect from the dissolution of local rocks (amphibolites, pyroxenites, etc.) and anthropogenic activities. Water was noncompliant concerning faecal contamination in 84.3% of the cases in the dry season (DS) and 96.37% of the cases in the rainy season (RS). The color, TH, TAC, turbidity, FeT, nitrate ion, and electrical conductivity values for some boreholes were outside the GDWQ values. Boreholes F8, F9, and F25 have very high Larson corrosion index (LR>1.2). The chlorine demand varies according to the season, ranging from 0.25 to 6.0 mg/L in DS and from 0.25 to 2.45 mg/L in RS. Regular monitoring is needed to ensure safe drinking water from boreholes in Kara.