Abstract
Many people in Africa depend on water from borehole, but purity of the drinking water from this source remains questionable. In a bid to ascertain the health risk local people are exposed to, this study analyses the physico-chemical characteristics of borehole water in Gassol Local Government Area (LGA), Nigeria. For this purpose, water samples were collected from the 12 administrative wards in the LGA. Two samples were collected from each ward, one in the rainy season (March) and another in the dry season (November), a total of 24 water samples in all. The water samples were analyzed for 18 different physical and chemical parameters to ascertain their comparability with the guideline levels recommended by the Standard Organization of Nigeria (SON) and World Health Organization (WHO). Results show that most parameters were within the guideline values in both seasons except for turbidity, pH, fluoride (F-), chlorine (Cl+), iron (Fe2+), ammonia (NH4+) and manganese (Mn2+). Overall, all of the wards had at least one instance in which a parameter falls outside recommended guideline. A further analysis using the mean value test approach to assess level of contamination relative to guideline values showed that the upper bound value (US95) of turbidity, iron, pH and chlorine are greater than their guideline values. This indicates that these are the parameters for which the most urgent action is needed. The high concentration of iron and turbidity outside the prescribed limits in the rainy season suggests that water managers need pay more attention to borehole water quality in the rainy season. There is need for further research across the region to better understand the quality and the contaminants (natural and anthropogenic) of borehole water so as to be able to proffer appropriate remediation strategy.
Key words: Groundwater, guideline value, mean value test, standard organisation of Nigeria (SON), World Health Organisation (WHO).
