Hydrochemical characterization, physicochemical and bacteriological quality of groundwater in Sidi Kada Mountains, northwest of Algeria

The present study aims to assess groundwater quality for drinking and irrigation purposes and to improve the comprehension of hydrogeological and anthropogenic processes controlling its chemistry. A combined approach of mapping major chemical ions and water quality index (WQI), multivariate statistics, and hydrochemical methods was applied to characterize the mineralization processes and groundwater quality. Water samples were collected from 36 boreholes tapping the Sidi Kada karstic aquifer situated in northwest Algeria and analyzed for physicochemical and bacteriological indicators. The physicochemical parameters of all samples are within the WHO guidelines, except for chloride. In addition, bacteriological analysis of water indicates the presence of total and fecal coliforms in some samples. The dominant hydrochemical types of groundwater are HCO3-Mg-Ca, Cl-Mg, and HCO3-Na. Application of the principal component analysis (PCA) underlines the contribution of Cl−, Na+, SO42−, and Mg2+ in the salinization process; reveals contamination of agricultural origin; and highlights the role of carbonate minerals and evaporites dissolution in the groundwater mineralization. Secondary processes such as cation exchange, silicate weathering, and anthropogenic contamination are showed to alter the hydrochemistry of groundwater. The computed WQI classed groundwater samples in two categories: excellent and good. Paradoxically, 20% of the samples showed bacteriological contamination while having a good chemical quality for human consumption. Nonetheless, groundwater quality remains suitable for irrigation purposes. This study recommends strict protection against microbiological contamination of boreholes used for water supply in rural areas.