Water Quality Assessments as Implication to Human Health:A Case Study in Awash Sebat and its Surrounding Areas, Afar, Ethiopia

Present paper reports the results of surface and sub-surface water on quality from Afar National State, Eastern Ethiopia. The area forms part of the main Ethiopian rift valley system and has long history of fluorosis problems. The geological setting of the area consisted of vesicular basalt, ignimbrite, alluvial and out wash sediments. Water sampling (11 surface and 13 sub-surface water samples) was carried out in January 2012 and analyzed for major and trace element contents using Atomic Absorption Spectrometer and titration methods. The major cations and anions in groundwater are present in the order of Na>>Ca>Mg>K and HCO₃>>Cl>SO₄>NO₃->CO₂, but in surface water Na>>Ca>K>Mg and HCO₃>>SO₄>Cl>>NO₃-, respectively. Among the cations, sodium concentration exceeds the maximum acceptable limit in about 25% of the water samples. The bromine and fluorine values in both waters are exceeding the maximum acceptable limit for drinking purpose. Bromine is ranging from 0.8 to 11 mg/l show higher values in all samples and fluorine ranging from 0.6 to 11.5 mg/l show higher values in 54.2% of the samples. High amounts of fluorine, visible in the area in the form of dental fluorosis, observed mainly in surface water samples, is contributed by Lake Beseka which is partly fed by Awash River. Data indicate that the surface water is suitable for irrigation and groundwater for both drinking and irrigation purposes. If surface waters are to be used for drinking, the excess fluorine contents needs to be removed using chemical coagulation treatment mechanisms.