Assessment of the water quality of selected boreholes in Mandera town and its environs

Abstract

Mandera town and its environs rely on boreholes, piped water, seasonal rivers and rain water for domestic use. Water scarcity and population rise in the county have made people rely more on borehole water. Increased pastoralism has led to increased pollutants that have posed a potential threat to surface and borehole water quality. This in turn poses a potential adverse health effects on the residents. This study was undertaken to assess the physical and chemical properties; investigate the presence of E-Coli; and compare these values with the WHO and NEMA guideline values. The study was carried out between October 2014 and March 2015 and a total of five borehole water samples were collected from five boreholes at different sites in Mandera Town, namely Mandera Town, Elwak, Takaba, Shimbir Fatuma and Banisa. Each of the five borehole samples were analyzed for pH, electrical conductivity, total dissolved solids (TDS), fluoride, chloride, nitrate, ammonium, potassium, sodium, lead, zinc and E-coli. The results were as follows : pH (5.1-7.67), electrical conductivity (840-6940 μS/cm), total dissolved solids (520-4302 mg/L), fluoride (0-1 mg/L), chloride (7.99-119.9 mg/L), nitrate (0.316-2.26 mg/L), ammonium (0-0.66 mg/L), potassium (4.7-101.4 mg/L), sodium (11.2-46.4 mg/L), lead (not detected), zinc (0.057-0.189 μg/L) and E-coli (nil/100 mL). pH values for all boreholes were within the guidelines except Banisa (5.1), Shimbir Fatuma (5.3) and Mandera Town (5.3) which were lower compared to WHO and NEMA standard (6.5-8.5). Electrical conductivity was within WHO guideline value (2000 μS/cm) except at Elwak (6940 μS/cm). Elwak also had a higher TDS (4302 mg/L) as compared to WHO (1000 mg/L) and NEMA (1200 mg/L). In all the five boreholes, fluoride, chloride, ammonium, nitrate, zinc, lead, and E-coli were all below the WHO and NEMA guideline values. At Banisa, Mandera Town and Takaba only pH did not conform to standards while at Elwak and Takaba all parameters conformed to standards except for electrical conductivity and total dissolved solids. No E.coli was detected in all the samples.